Back when we purchased our first RV (used Montana fiver) there was a Montana owner who did live in his year around in AK. You might go over and check the MOC (Montana Owners Club) forum and see if any of their contributors recall details from stuff he posted back around 2010 or 2011.
I'm certain you will have to not only skirt the bottom in, but you will no doubt have to insulate it as well down there, just too much exposed plumbing. Either the gate valves will have to be super insulated with a heat source or you will need to at least insulate them and use RV antifreeze in the toilet instead of just plane water is my guess.
It is one thing to stay in an RV with temps between 0 and 30 degrees for a couple weeks in the lower 48. It is a whole different thing to spend a dark winter in AK in an RV IMHO.