how will our lives on earth change once we make first contact with space aliens?

It depends on the aliens. Are they friendly or hostile or neutral? Can we communicate with them? How much further advanced than us are they? Are they so advanced that they are Godlike? Are they biological or machines? Are they conscious? Do their thoughts run at same rate as ours?

The question is irrelevant.

Even if space boogiemen exist (and all indications are that they don't), and even if they could achieve the physically implausible task of crossing hundreds of trillions of miles of cold, hard, irradiated vacuum to get here, then why oh why would they bother with a planet crawling with pudgy, savage little space monsters that consume everything in their path as they swarm across their planet? Surely they would choose a world with beings at their own highly developed level. Seeking "contact" would not in any way shape or form be anywhere on their agenda.

So unless you are going to write yet another one of those tedious stories about space aliens being somehow magically drawn to Earth, and doing anything other than totally ignoring us, then there is no point even considering the situation.

Not at all, unless they choose to share some technology with us.

They would not be stupid enough to come and visit us - and they live hundreds of lightyears too far away anyway

There is a basic false assumption in your question. It should read "...IF or when we make contact...."

They’ll pickle us and put us in 500 gallon bottles for snacks.

There is a strong argument that we will be extinct by the end of the next century but the argument doesn't furnish us with the cause. If aliens make contact with us over that time, that could be significant in that respect. For instance, the very fact of awareness that aliens exist might cause so much unrest among us that our societies will implode and we won't survive, or the contact might involve some kind of technology or pathogen which will cause us to become extinct. One thing we can confidently assert is that we will never be living among the stars, so whatever happens, first contact will not lead to humans like us settling in space beyond this planet in any significant numbers.

chromedomes who have gotten the galaxy commuting thing down pat 30 million years ahead of us understand terran 2 leggers are 30% wacky and unpredictable,and may have us on a noflynonuttin list.

2 world wars in the past 100 years,add deaths due to forced starvation,,among stalin,hitler,mao,a hundred million were plugged & buried, starved to death,eventually.
alien concern primo uno. about us here,.'if they get the wherewithall to travel like us,we could be next', aliens debate whether to shoot an asteroid sized 30 cal M! garand at us.

perhaps first contact in the past is responsible for humans today.

It will never happen since ET UFOs dont exist.

it depends on the  ALIENS..

SINCE THEY CAN  travel  light years  faster than us ..  and since we are likely to be less inteligent then them ... 

ask a NORTH american indian what happened when they  GREETED   the  europeans nicely

When, or probably IF we ever make contact with an alien race there are two possibilities.

1) They are benevolent and they will be happy to share their technology with us and help us overcome our differences, medical problems etc.

2) They are malevolent and will probably have the technology to take over the planet and us, or simply quickly destroy us.,

We will wake up and stop Fighting

Well, the ones that post here saying there's no one out there *might* stop...  Or, maybe they'll just resort to their presence as a new conspiracy theory....  
How life changes will depend on the aliens.  Are they violent? Are they charitable? Are they simply cataloging our planet?  Do they regard *us* as being intelligent?  

I would bet our government and armed forces would look for a means of protecting ourselves - regardless of how 'peaceful' they would appear. I would bet there'd be some panic and chaos at the beginning of their appearance - and, it may get worse or better depending on the nature of the ETs...

I wouldn't count on it, in all mans existence on earth, had we radio from the beginning, our transmissions would just now be reaching half way across the galaxy.
I thing you underestimate the size of the universe here. Sort of a pet notion our ETs have been here a long time, I mean take a gander at water bears/moss piggies.
Those little guys certainly didn't adapt to the harsh conditions they survive in here on earth. They will be here when everything else is extinct.
https://featuredcreature.com/bizarre-world-of-moss-piglet/

There are no "space aliens". Star Trek was just a TV show.

They will serve us in their margaritas!!

If the aliens are friendly, we could get to know each other by starting cultural exchanges, open diplomatic relations with them and maybe even build an embassy for their ambassadors. If they’re located on a nearby system, perhaps we can trade with them. Thousands of aliens goods will be shipped to Earth and we will ship out Earth products in return. People would be able to visit their home planet and they could visit Earth. The tourists industry would benefit from this.

Humans would be like the Aztec. If earth history is any indication. The higher civilization always dominates to a degree or other, the weaker one.

But we may benefit from new knowledge in a good relationship. That's not the norm on earth.

Mass panic and mob psychology. i suspect first contact was already made in July 1948 if not much earlier. I think the entire Solar System was quarantined until we grow up enough to become civilized enough to kill each other for power, lit, mony an entertainment. Civilization is a very thin veneer that disappears pretty quickly. Look what happened in greater New Orleans after Katrina. Almost anarchy. 1740 deaths from drowning followed by shootings, self hanging  and suicide by cop. And then there's death by microbes, pathogens, 

The general public is NOT ready for first contact. 

Badly. We will be harvested for crude protein.

Space aliens and UFOs to me are fallen angels as mentioned in the Holy Scriptures. "Woe to the earth, because your adversary the devil has come down to you." Read a little Bible Scripture and find wisdom. Revelation 12:9 kjv
"And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him." Verses 10-12 "And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of His Christ: for the accuser of our brethren is cast down, which accused them before our God day and night. And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death. Therefore rejoice, ye heavens, and ye that dwell in them. Woe to the inhabiters of the earth and of the sea! for the devil is come down unto you, having great wrath, because he knows that he has but a short time." One thing the devil does is that he teaches many ways to make war. His purpose is to kill, steal and destroy. How does the devil know his time is short? Because he knows God's word and the Devil (Satan) believes in God, not like some unlearned men of today.

People would become united.

They will teach us how to pee out our fingers if you ever saw Scary Movie 3 LOLggghhhgfffggh

Fantastic! The first thing we need to ask them is how they accomplished a 30,000 year mission to reach us? Wow! How did they even know the correct direction to travel?

Or? "Well we would have been here 4,000 years sooner but 'half looped' Louie took a wrong direction turn at Andromeda."

That would depend on how we contact them.
By radio or have them land on the front yard.

That rather depends on the aliens.

Be controlled like we are now they will clearly take over with ease. And do as they please kill us in slave us what ever they wanted 

There would be mass panic. Mass anxiety neurosis.

Of course, some people would be cool with it.

Space aliens will never make contact with us becuse it would violate the prime directive.
OK, they really would never make contact with us because they are not stupid enough to want to associate with a species that has no real intelligence.

Or they might invite us over for dinner.
https://www.youtube.com/watch?v=NIufLRpJYnI

We will probably all die from the bacteria they bring with them that we have no immunity to and we shall all die.

Idk. There will be mass hysteria. People will worship the aliens. Also, chances are that some of us will travel with the aliens back to their home. We'll share technology. The type of aliens that are good won't colonize us. The type that are bad will destroy themselves before they even get here. Lol good right?

I think on the contrary , when the aliens contact with human being on earth ,they would change from having black hair in to white , when hearing that, during the last Century, mankind creates World Wars twice and kill each others mercilessly , in millions and millions , especially in the Western Regions of the world. I HOPE THEY WOULD SWARE NOT TO COME BACK TO THE WORLD AGAIN.

has , not will .