Smokeybear,
1. Season the smoker prior to using it.
2. Salt is correct, the factory thermo is generally pretty lame. If you can use a couple of thermometers. One for smoker temp, and a 2nd for meat temp.
Lots of us use the Maverick 732 sold here on SMF, and mine does fine. However, the sell thermos all over the place. Pick one or two you like.
You should be fine on a 20 # propane tank for at least 2 good smokes, especially if you are cooking really low (200 - 225 degrees) u=nless you have wind, rain, snow, or some other variable pulling the heat off your smoker. You can always make a wind break, or shelter if necessary. Some folks use foam insulation panels, plywood, or sheet metal to block the wind. I am fortunate I can move mine around, but I know a couple of people that cook in their garage during bad weather.
Use the search function on SMF if need be.
You are going to get great results. Remember practice, practice, practice. You know the drill! Go get 'em!