What would cause a sudden loss of radio, gauges, a/c, dome light?

Checked fuses and for loose wires. What has me confused is the things that quit working are all powered differently and have separate fuses.

That was first thing I did but all were good. Someone said might need to have computer re-flashed at dealership. Does that make sense?

I had a 08 GMC in the shop just last week with a bunch of crazy elect. problems, now on this truck the problem was in the black fuse/relay center under hood on drivers side. It had poor connections under the the top panel. There are tow locking handles on each end of this panel, top cover removed, you can lift these handles and push them back down to see if that may tighten the two halfs of the box and make a better connection for the fuses to wires. Don't try to lift the top section out, just raise and then snap locking handles back into position. If no luck seek a mechanic with a good scanner! Yes, scanner will help,