The electrical wires in the first photo look original, but I don't know what they went too. One is probably a "hot" 12 volt
line, the other the ground. If you connected them together you most likely blew a fuse.
The wires going to the round electrical box may not be original, as I don't recall Airstream ever using a round metal surface mount box with a cover in any of their electrical work. I have no idea from the photo what they could have gone to or been for.
The third photo shows some kind of a 12 volt
fuse, but again no idea of what it was for, most likely not original.
The tambor doors under the front couch can be removed (may or may not be easy, look for screws in the plastic track on each end) and new canvas or heavy muslin put on the back with spray on adhesive (leave the end half inch un covered so they slide in the tracks better) and re assembled. I am sure there are threads here on the forum with detailed instructions on how to do it best.
The clock most likely has a battery in the back of it. You will need to take the panel out that holds it, probably two screws showing somewhere.
I would guess the thermometer is an old mechanical one, with a long capillary tube to the outside somewhere. Most likely broken capillary tube. Little chance of replacement. New digital ones are under $20, and the easiest solution.
I am sure there are threads here on how to repair the cracks. You can stop the spread of them (usually) by drilling a very small (1/8") hole at the very end of the crack. I can say that Krylon Fusion for plastics spray paint (white, satin) will work wonders for making the old yellowed plastic look like brand new. The refrigerator vent, end caps, and often the AC interior cover all can benefit from that wonderful spray paint.