2011 Silverado LTZ Body Control Module issues?

I purchased a 2011 Silverado LTZ 5.3L V8 a couple months ago for fairly cheap. I knew it had some issues and I generally have no issue diving in and getting to work. I’ve replaced the oil pressure sensor, upper control arms, lower ball joints, drum brakes, a headlight pigtail, taillight circuit board and the washer pump.

I ended up taking it to a garage to be diagnosed after replacing the circuit board and the washer pump. When I bought the truck the drivers side turn signals didn’t work (taillight, headlight or mirror) and the brake light was also out and the window washer pump didn’t seem to work. The wipers would turn on when activated but no fluid would come out even with a full bottle.

The replacement circuit board seemed to fix my issue with the taillight and I got my blinkers back on the taillight and mirror (but not the headlight) but the washer pump still wasn’t working. I took it out and tested it and the unit itself is fine, but it’s not getting power from the vehicle. About a week after replacing the circuit board, my turn signals and brake light stopped working again. Long story short, I can’t figure it out so I took it to a garage (I’m not a mechanic, I’ve just been working on my own vehicles since I was 16 to save money). He didn’t have the tools necessary to do this repair, but he said he believes that the electrical issue is caused by the BCM.

I can buy a preprogrammed one online for about $200 but it says I may need to take it to a dealer for reprogramming, Something about the airbag or something. I called the dealer for a quote just to have them do it and it was coming in at about $800 for parts+labor. So before that much money, could it be anything else? Is there a way for me to diagnose it at home?