if changing cid is required,you will need the phone to be s-off as well. simply bootloader unlocked doesnt allow alot of changes.
the best way to unroot is simply:
1)restore an unrooted backup
2)re-flash a stock recovery if needed
alternately,you could track down a stock rom and flash that if you dont have a backup,or you could run an ruu,if one is available for your build.
if you have only installed superuser and not flashed a rom,then you could always use a root explorer to navigate to system/xbin and delete the superuser file,and then simply delete the superuser app. if youve rooted with superSU for superuser,it has a built in option to unroot,just open the app and use that.
hope that helps