Welcome! I'd honestly be surprised if there were any leagues up in Killeen but there is a group here in Austin that holds tournaments fairly regular. The group is Bat City Pinball.
Facebook: https://www.facebook.com/groups/BatCityPinball/
Website: https://batcitypinball.weebly.com/
Seems like they're having a tournament tomorrow at Buffalo Billiards downtown tomorrow. I haven't been to any of their events yet but I really should go sometime.
My brother play_pinball just finished shopping out a STTNG so if you have questions while shopping it out he might be able to help. One of the wiring harnesses to the cannon on his game has a break in the wire so we're waiting for that to arrive and get swapped out so that we can actually put some games on it. He actually ordered a spare set of harnesses so if yours needs replacing you might be able to buy that off him. If the wiring harnesses for the cannons haven't been replaced yet odds are they need replacing. They're apparently very prone to failure.
As some general advice when shopping something out I can't stress enough to take lots and lots of pictures. And after you think you've taken enough and you will have no problems getting that piece back together once you take it off... take some more pictures. You don't want to be sitting there trying to put your game back together going "How did I not get a picture of this?! How does this go back on!?"
If you need help with anything feel free to message me. I typically do my own board repair though I'm no expert.