I want to upgrade to windows 8 but I have A LOT of questions

1. Is there any compatibility issues I should be afraid of? Like with steam games, my logitech mouse, wired xbox controller, divx, itunes, spotify, etc?

2. I definitely don't want to do a fresh install (mostly because Ill lose everything if i do), so is a upgrade on top of windows 7 advisable, or is it a bad idea?


3. Do you need your windows 7 disc to upgrade for 40 bucks, or do you just need windows 7 installed on the computer?

4. Does windows 8 perform better or worse when it comes to ram; do you need more ram to do things on windows 8; is windows 8 any faster or slower than 7?

5. Will my folder setup remain the same, or will things move around if I upgrade?