And you want to change it up to stock? Do you have ROM Manager Premium? If not...get it...the few bucks is WELL worth it.
Then you could just download and flash Bugless Beast with a stock theme over top of what you have (when you go to download BB, you will get all those options to choose from). Should be pretty easy. I think you'll be okay to load it over your existing installation without wiping data...but wiping data is always the recommended way to go.
If not using ROM Manager:
You could also load the same ROM through whatever recovery you are using. If using Clockwork Recovery, you just place the .zip file on the memory card (anywhere you can find it...the root of the SD card is probably the easiest) and boot into recovery. Choose "Install ROM from SD Card" and then find the file...done. If you want to wipe data, that is just an extra step and you will see it when you boot into Clockwork.
If using SPRecovery, you can just rename the same .zip file to update.zip and then you click on Install > Allow update.zip installation (nothing appears to happen...but something does
) > install update.zip (depreciated). Again, wiping data is just one more step.
Does that help?