Welcome to the forum David. What method did you use to root?
If you want to unroot, use odin to install the stock UVUAMDL rom
. See how your phone works. If its ok you can try root again. If its still having problems and you want to take it back;
You need to be on the stock rom and stock recovery. If you don't use TA, system status in Odin mode will show Custom and also Device Status in settings will show Custom. You don't want that if you have to return your phone for some reason.
1 - Odin stock MDL rom.
2 - Use CF-Auto-Root from the XDA thread
. Just install it through PDA in Odin. (see his 2nd post for instructions) Now you're rooted with stock recovery so you can use Triangle Away.
3 - Use Triangle Away
. Follow the directions exactly.
4 - After phone reboots, go back to stock recovery, do a factory reset and wipe cache partition.
Everything in Odin mode and in settings About Device should all say Official now.