where should i go with my wife for a one week vacation? Italy, France or Spain? and how much would it cost? and also the weather?

I can highly recommend Italy - beautiful art, architecture, scenery and music, interesting local festivals, great people and food. Beaches, mountains, lakes, the ocean, historic sites, world class museums and galleries and a lot of varied things to see and do. The best part is the wonderful Italian people. It's very easy to get out and explore Italy and further in Europe using the trains or budget flights. Mid-April to mid-June or September to October are good times to go. The peak summer season can be very hot and crowded

Nobody can tell you with any certainty what the prices will be like that far into the future. Prices depend on exactly where you're starting from, when you go (prices vary a lot), how long you stay, where you go in Italy, how you get around, the kind of places you stay in and what you see/do/eat. People who backpack generally can get by for $100 per day staying in cheap hostels and carefully watching their budget (not including airfare). However, if you stay in hotels, it will cost you more. I usually spend 100 to 150 euro a night for a hotel just for myself, but there are cheaper places.

Here are some resources that can help you plan and check options and current prices for your trip (expect prices in the future to rise):

http://www.kayak.com/ - airfares & hotels; the explore function is useful for finding the less expensive places to fly into from your starting point.

http://www.trenitalia.com/tcom-en - Italian train schedules & prices. You can find links to the various national train sites on the Man in Seat 61 site above.

http://www.venere.com/ - hotels/B&Bs - prices for the same hotel can vary hugely depending on the season and what local events are going on.

http://www.hostelbookers.com/ - hostels.

http://www.monasterystays.com/ - monasteries & convents that offer accommodations

You can also look into camping or couch surfing as cheaper alternatives for accommodations, but you don't need to with your budget.

http://www.backpackeurope.com/ - information & advice

For sightseeing prices: check the websites for entrance fees for the museums & galleries you're interested in. I spend anywhere between nothing and 40 euro a day depending on exactly what I go to see when out exploring. For food, I spend around 25 to 50 euro for a meal, but you can eat for less. A pizza is 8 to 13 euro and a panino or wrap is around 3 to 6.50 euro in many places. You can often get food at festivals at a relatively low price. You can also shop in the markets and put some meals together for yourselves. When I travel, I like to try the local specialties and the good restaurants.

No one can guess at what it would cost you, as you give no specific dates and you failed to say where you would be flying from.

Go on some booking sites, and include where you will be flying from, and what specific dates you want.

A travel agent can help you decide which destination would be most pleasurable for you.

That depends what interests you. Many people want to see the Eiffel Tower and other sights of Paris, or the historic sites of Rome. As for time of year, Paris is cold in the winter and rainy in the spring. Summer months are best. Southern Italy and Spain are much warmer and really too hot in the summer. They are better in the fall and spring.
If you would enjoy using your Spanish, go to Spain. Barcelona is particularly interesting. In the summers, everyone congregates on the beaches of Spain, which is probably where you'd find the most nightlife. But you can get by easily in Paris or Italy with English. In fact, if you speak French to people in Paris, they answer in English!