What you want to do is very feasible. I have been involved in three businesses that are key to your idea - first in the wood stove/solar business and now in the spray foam insulation business.
Full-timing in that climate will make you aware of ALL the deficiencies in your bus in very short order. In order to produce a conversion you'll be happy with over time, I recommend the following:
1) Remove all the school bus windows, raise the roof and re-skin.
2) Install a limited number of double pane RV windows
3) After figuring out wiring and framing, insulate the whole thing with 2 lb. closed cell polyurethane spray foam. I'd suggest 5-6 inches in the roof and 3 in the walls. (Raising the roof allows you to put in adequate insulation and still stand up...)
4) Insulate the floor. For that kind of climate, I'd seriously consider spraying 4-5" of foam underneath the floor and protecting it with spray-on bedliner.
5) To help offset short winter days, put AT LEAST 1000 watts of PV on the roof, with charge controller and batteries sized accordingly. Needing shore power will really narrow parking options and running a generator is both cost prohibitive and offensive. My goal would be completely off-grid.
6) There's a lot less oxygen at elevation, so remember to de-rate the output of any combustion device (including wood stoves) by 3% per 1000 ft. elevation.
7) As with everything else at ski areas, firewood is usually rather expensive. Get a new EPA approved wood stove with "secondary burn". This, together with proper insulation and minimal window area, makes comfort possible/affordable.
Finally, install all tanks and plumbing INSIDE the thermal envelope created by the spray foam insulation. No plumbing in the exterior walls. Strongly consider a composting toilet to eliminate the entire issue of black water.
If you do these things, you will be VERY comfortable living at elevation in the winter. If you skimp on anything on this list, you'll probably have regrets every evening when you come home to it.
This should be a very cool build. I'll be watching!