I know it suggests it can delete an sd card, but what's the chances of messing up rom?
Very low, even if something does get needed up you can just reflash your rom. Just make sure you have a back up if your phone and your sd card just in case.
And don't freak out if you think you bricked it you probably didn't. Just keep trying, if you run into trouble get on IRC and the devs will get you through it.
Sent from my HTC Evo V 4G