If you're going to make this truck run, you'll need some tools, namely a subscription to ALLDATADIY.COM that tells you about your truck, DTC codes, wiring, etc. Then you'll need a code reader that will read all the computers in your truck and erase the codes also. I currenrtly use Bluedriver which costs $100 and will even work with my Mercedes, but there are lots of capable readers on the market, from $20 to whatever you want to spend. Make sure your batteries are fully charged before working on it and remember that every electrical device, motor, sensor, etc also has to have a properly working circuit to support that device. When you read for DTC's I'd likely go after any U% codes, get everything communicating first, then pick another code and see if you can fix that one. It often happens that fixing one thing also fixes another 2 or 3 things.
Best of luck to you
2008 Silverado LT, CCLB, Edge Insight CTS
2009 Arctic Fox 29-5T, Silver Fox Edition, Onan 3600 LPG generator