Root G900-A root question

[jackroo]

Merry Christmas to everyone. I just got an unlocked Galaxy S5 G900-A that was originally set up for AT&T but am using it on Metro PCS. I set up the apn settings and I want to root it as its running 4.4.4 and it won't allow me to do OTA updates. I've read if you're not careful you can re lock phones by flashing the wrong stuff. What do I need to be careful of this time around and what carrier or non-carrier specific roms should I flash? Thanks