Jesseannie, a few things to keep in mind. Platinum Cats are pricey, but I don't know another vented propane heater, catalytic or other, suitable for small RV. You will need their 5000 BTU model for a trailer of that size. Their vent kit comes in 2 varieties - directly through the wall or with flexible exhaust hose running to wherever you need it to exit. Photos above show cabinet-mounted heater with exhaust hose, but when mounted on the wall, you'll exhaust directly through the wall. I believe Arnie of Platinum Cat can make the propane intake fitting to where you like it, either on the bottom or on the side.
What Johny said about AZ dust, is true. Catalytic heaters can get clogged with dust and should be covered when not in use.
In terms of solar, this topic is too wide, but in power-saving mode - no microwaves, toasters, 120V coffee makers - and with something other than furnace for heating, 180-200W panel is sufficient. In winter it will harvest about 15 AH on a dark day, and 50 AH when it's sunny. With size and cost being essentially the same for 200, 230 and 250W panel, I would get 250.