Default [Q] Can I reflash with full 4.3?

Completely stock T-Moblie SGH-T999 phone. Ever since the 4.3 OTA however there has been some visual corruption in the notification pulldown (along with a few other issues, even some hardlocks) and simply clearing user data does not correct it no matter how many times I try.

So I'd like to try flashing the whole MJC rom via Odin in case something went wrong with the OTA. However while I am comfortable with Odin as I used it many times in the past with my SGS1, I am understandably a bit wary of this whole Knox thing. Will I run into any issues attempting this? Life was so much easier before secure bootloaders lol. I don't want to try this and accidentally brick it. Any insight as to whether or not I should even attempt this would be greatly appreciated! Oh, and if it is OK do I need to remove SIM while doing it?