That's a little more tricky.. there are a few Roms that are stock with little to no tweaks I would suggest over your current stock rom (and they are more stable too). Once you are rooted, download titanium backup and back up apps only..that way you can restore them to their current state on any rom
As far as restoring your current stock, you just gave to flash the appropriate Ruu (located in the one x index on xda) and flash it... I do believe that will relock your bootloader once you do that- not 100% on that seeing as I've never wanted to go back haha