the jelly bean rom you have on there now is a port from the jelly bean preview that came with the io copies of nexus 7. it's not official, it's experimental. there are jelly bean roms being built from source now if you're interested, you can check out dmmarck's jelly bean now thread stickied up top.
the options i have you are basically manual vs automated. the worst part about all of this, if you're on a pc, is setting up the drivers correctly. wugs will do it for ya, you just have to input a few things and it does it. if you're interested in reading up on it, the manual option is cool and not that hard, but if you just want to go back to stock and forget about this whole root/rom/bootloader business, just use wugs and don't think about it again
i'm not sure, but wugs may not relock the bootloader for you. if it doesnt, it's very easy to do and you can check out cyberwarrior's (or dmmarck's i forget) thread on locking/unlocking the bootloader for that.
so that's that, any questions of course feel free to ask in here or in the respective thread for whatever it is you get stuck on or need clarification for.

gl