Edenaluuk

Hi, anyone have electrical insight on a 99 Silverado Z71 LT with a 5.3 Vortec. A previous owner had a remote starter and theftlock bypass installed and in trying to make that actually work I broke something (I've now removed the remote starter and bypass module). My courtesy lights, message center security light, radio, power seats, etc. all work. I can start it and drive too. What isn't working is the gear indicator (light showing park, reverse, drive, etc.), my HVAC system, my ride selector (4WD or not), or gas gauge. I was thinking it's my BCM but due to the specifics I'm thinking my mid bussed electrical center. Any ideas? Thank you in advance!