2 last questions

Both z4root (2.2) and the new GingerBreak (2.2.1) have the option to unroot thereby saving your rear in case of warranty support, lol. Just note that if you delete system apps, you'll have to flash your phone back to stock and can't simply unroot. Not hard, just will take you an hour instead of a few moments.

If you root first it's in-place and will not delete your info, however Gingerbreak occasionally deletes SD Cards so back it up. Once rooted, you can find several backup apps available on the market. Some people just 'google' Titanium Backup Pro. It can backup and restore apps without issue.

 

Backups will save your personal data/apps/games. Deleted system apps don't restore willingly, hence why those who stay stock just freeze them. If you want to stay stock and delete them, this is where a flash will become necessary.

If you go all in and do the setup for a ROM, make sure you follow the tutorial on how to perform a NAND backup as this is the truest ass saver if you venture into it. And for the love of Pete please do not use ROM Manager.