Boot into recovery and make a backup.
I have a thread for rooting and/or downgrading back to GB that is very user friendly, so give it a read to become familiar with Android flashing and rooting. I'll link you to a CM10 rom shortly as I'm a little busy right now, but you really should do some reading before doing anything, otherwise you may run into trouble and not have the knowledge of how to deal with it should a problem arise.
*Sent from work early bcuz some1 4got teh NSFW tag*