in any troubleshooting, it is easier to start from simple and work its way into more complex... naturally, the fuses come first...

Do you have access to WDS wiring diagrams? you would look at the items that have a problem, and when there are several items glitching, the issue is probably cntralized in some module or a wire - wires are harder to trace... the GM has a half a dozen fuses coming in, and if one fuse is blown, the electricity finds its way to the affect circuit by other paths and the things work totally unexpected - i had wiper fuse removed, and interal lighting would come on... or something to that effect... lol...

get your symptoms organized - see what can you find that is not working, and look for those fuses... if fuses are ok, then look for GM...

I am at work, can't look up the WDS but you should be able to - at the top of every page is ONLINE REFERENCE, click on it, follow to X5 diagrams...