There is one other possibility for the AC problem. After going back and forth with the dealership about the same thing you're reporting, the mechanical side of the dealership gave up and sent the truck to their body shop. Turned out that after the body shop pressurized the cabin with a vanilla scented smoke/fog they found a leaking seal or joint in the body that was allowing water to get in and run down to a spot that made it look like it was the a/c. I had just had the a/c rapaired and that's why we chased that dead end for a while. I wasn't there to watch all this, so I'm not exactly sure where it was leaking, but they fixed it and it's been fine since.
The headlight switch is easy to get at by just removing the plastic trim ring that goes around the whole dashboard. It will expose the three small screws that hold the switch in place. I've tapped into one of the wires on the switch to run my gauges on the dimmer, but never totally taken it apart. Doesn't seem like it's too bad. A buddy had to replace his and he was able to do it pretty quickly. TDR screen name isb360 if you want to ask him. good luck.
Just read the post about 3rd brake light-got posted while I was typing this. That was what the body shop orignally thought was going to be my problem too. They said that wasn't it in this case, but that is was somewhere else. I had forgotten all about that until just now.