I don't know if it does heat, you probably need to investigate the model number and call Coleman,
AC are run on electricity, 110v, only. I may be wrong but I don't believe there is a gas powered AC for Airstreams.
When you mean reseal, do you mean the joint where the pan meets the roof? Use parbond, I believe, kind of like caulking a bath tub. OR...even better, for the future, use butyl tape, like you can get at RV stores, and lift the AC off of the roof a bit and get a ribbon of that tape all the way around, where the pan meets the roof. It'll stay pliable and you can get it off easily 20 years down the road when you switch to a Carrier. I'm just guessing a bit here on this one, so if others have better ideas, do with them.
Or avoid all of this and get a new Carrier 13.5k with a heat strip. No sealing necessary and they work like a charm. It's what we did.
That's not me in the picture, see the Otisville rally thread to understand what's going on...I don't even understand....I think those people were gassed or drugged at that rally!