Default How to update 4.1.1 t-mobile to newer firmware

Hello everyone, Sorry for the n00bish question but i've been out of it for a long while. I have my i747 unlocked and rooted running on T-Mobile with 1700 band enabled with stock ROM. Whats the current best/safest way to update to a newer firmware 4.4.2 or 4.3. Thank you ahead of time for pointing me in the right direction. I tried lots of searching and reading but cant find much. Thank you.