The first thing you need to do is unlock your phone (
use Hard-SPL).
Then you can flash your phone.
It's pretty painless, plenty of ways to fix a bad flash.
The rom you get depends on your needs.
Mighty Rom is pretty barebones, maybe something you want to start with.
Each rom's thread should also have rom specific installation instructions and FAQs.
Also remember to install the proper carrier provisioning and fixes for the rom you ultimately choose to get full functionality.