I am far from an expert on this, I have however been reading about folks doing it for years. Heres my thoughts
Get an adapter and a much larger propane tank. Will need a dealer to get a big tank. The propane heater in the camper sucks propane really bad.
Skirting, I have seen haybales, foam insulation, the list goes on. The main thing you will need to stop the underneath from getting any cold air. I think the skirting is the most important part for you.
You will need some type of heat for the underside, probably electric. You have to keep the underside warm.
As for water and sewer you will need heat tape on both. They make a water hose with heat tape built into it.
You have a project ahead of the cold weather.
07 Meridian 36G
Roadmaster tow dolly
Great Wife!! & Max the Frisbee chasing dog.