Keystone in 2012 and 2013 montana units used a 2 inch or so flexible tubing off the furnace that they threw down into the general area of the black and shower tanks, hence heated tanks. So you want to use the furnace for your main heat in the rv. People in various campgrounds across the country that I have seen, apply large fiberglass wool ducting meant for houses over their sewer hoses and use heated and insulated water line. Some on here noted that they ran a small ceramic cube heater in the pass thru to help provide heat into the belly of the beast. Propane use will be higher, so getting a larger tank dropped beside the rv from a local provider would be a welcome addition. Other than that you should be able to winter in it.
2012 F350 6.7 L dually, 2013 3800RE with 6 pt leveling, Sumitomo 17.5" load range h tires, Samsung 18 cu ft residential fridge, 8k Morryde I.S. with disc brakes. Full timing since 2012.