(update)My 2006 Mountaineer has been sitting vacant for several years
My son and I spent two nights in the camper over the Memorial Day weekend. I first changed out the marine battery with a charged one I brought. With fingers crossed, we watched as the DC power light came on. I turned on a few light switches, then hooked up the big four prong cable to the side of the RV and plugged into the RV specific receptacle on my pole. Success! The AC cooled nicely for both nights and the refrigerator/freezer worked perfectly. I did not get around to checking out the propane system yet but will do that on the next trip. Most of the time was spent cleaning and removing the old bedding. No sign of rodents as most every drawer had bowls of poison, but there was a shed snake skin just inside the door. This may have been a good thing to keep the rodents out. I still have a lot of cleaning to do and need to put on a new vent fan cover. All in all, I think the camper will be useable for another season. It will never be moved from this location until I eventually sell it. I will be building on the site and will use the camper as a temporary camp. Many thanks to all of the kind people for sharing such helpful advice. I will continue this thread as things develop.