Winter RVing can be tricky. I don't use my water system in my truck camper in winter and I carry two 20lb. propane tanks, have a 18,000 btu furnace, 2 AGM batteries and a 2000watt Honda generator and my truck is 4X4.
The Walmart in Sandy Utah is open 24 hours and allows RVs. I have also parked overnight without hassle in the Ski Bus ($5.00? round trip) parking lot. There is also a Sandy Community rec centre across the street with pool, spa hot tub, and sauna for about $5.00.
For Aspen I plan on staying at the open year round campground in Basalt.
Jackson Hole area does not allow overnight RVing and no year round campgrounds that I am aware of, however because summer is the main tourist season and winter is the off season there are some cheap accommodation in the town of Jackson (about 20min. from the skiing). I will be staying for a week at the Motel 6 where it is $50/night plus 30% off for a week long stay so it works out cheaper than some campgrounds. The rooms are small but recently remodeled and there are enough rooms that I will not bother to make a reservation. You can drive to the Stilson Shuttle Lot, about halfway to the skiing, day park for free and take a free shuttle bus to the skiing or catch a ski bus ($5.00?) from in front of one of the hotels in Jackson town. Or pay $15/day to park right near the lifts.
My itinerary is to show up at Snowbird/Alta just after Presidents Day for a few days on my MCP and then on to Aspen and then a week in Jackson Hole to coincide with the EpicSki JH Gathering Feb. 26 to March 6.
Hope this helps.