Les,
My idea of how to winterize the coach is to live in it in Key West. Has worked great so far, so take these thoughts with that in mind
I think number one is to keep water from freezing and bursting very expensive things. If you have no plans to try and remove the water and replace with an anit-freeze you will then need to keep things somewhat above freezing. Seems to me Newell has some pretty good options for doing that. Our coaches are about the same vintage. In my basement utility compartment with the tanks and pipes that are two heaters. One is electrical and the other is off the AquaHot system. Since it sounds like you may not have very good electrical options you might want to consider having a full tank of fuel and running the AquaHot. It should keep everything warm both inside and in the utility compartment if you set your thermostats correctly. No need to keep things tosty, just above freezing. The AquaHot does need electrical power to run the blowers and circulating pumps and it gets that from batteries, but you will need to provide some method to keep the batteries charged. Be sure you inverter has a low setting for current consumed to avoid tripping the breaker feeding power to your coach. Once setup I would arrange to visit often, or have someone do it for you, to insure fuel levels and battery charge levels are where they should be, as well as to check temperatures. You can get very inexpensive thermometers that will store the max and min temperatures and I suggest putting a couple of those in places of interest and checking after a very cold period. The cost of say a burst heat exchanger in an AquaHot will justify taking extreme measures to be certain you keep things warm. Good luck. Russ