I root all my devices within a few hours of buying them
To root, file the OP in this thread http://forum.xda-developers.com/showthread.php?t=1695238. It is really simple. Just follow the instructions and you will be fine.
Your warranty is void but it is a simple case of downloading a stock ROM from www.sammobile.com and restoring your device to stock of you need to return it for whatever reason.
You will then have access to any custom ROM, root only app, etc...
If I want to change back to stock ROM or upgrade to official ROM do I lose whats on the device currently (app settings, phone settings, photos, videos, sms's, etc)?