8 gigabyte - between 1000 - 2000 songs, depending on the bitrate and length.
Connect your iPod to the computer > open iTunes > check the box that says "Manually Manage Music" > import your music into iTunes > drag and drop the files into the iPod. From there you can create playlists to organize the music. (Manually managing the iPod ensures you will never lose your music. If you accidentally delete all the files from your computer, you automatically have a backup on your iPod and can transfer the songs back to your computer. Since you're new to iPods I HIGHLY recommend you use this setting.)
You can buy headphones anywhere - Target, KMart, Wal-Crap, Radio Shack, et cetera. They will cost anywhere from $10 - $100 or more.
I personally prefer Philips Virtual Surround Sound (
http://www.amazon.com/Philips-SHE5910-Virtual-Surround-Headphones/dp/B000QS4FMA/ref=sr_1_3?ie=UTF8&s=electronics&qid=1219540257&sr=8-3) I purchased them from Wal-Crap six months ago for $14.95 and absolutely love them. They have incredible bass and the sound is crisp and positively delicious.
Yes - you can use Limewire to download the music but you'll have to use iTunes (because you will want to manually manage your iPod) to add the songs to the iPod.
iTunes is pretty much the best application for music. You can import music from CDs, add lyrics, album art, change the equalizer settings, rate the song, et cetera, et cetera, et cetera.
I hope this helps.
Good luck.
參考: Savvy.