It took me a couple of times to figure out what I was doing wrong but it worked perfect with everything showing Official. 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.