Having done this a few times over the years, the extension ladder is pretty easy. As others have pointed out, use a towel/piece of rug to protect side of RV. Leave the air conditioner in the box to help prevent damage. I placed the box onto a piece of plywood slightly larger than the air conditioner box, secured box to plywood, drill a couple of holes in plywood for rope( similiar to a "Y" connection). You want the extension ladder to be right at the same height as the roof of the RV thus you having to pull it up over the rungs of the ladder(thus sliding right onto the roof.)
Ok....still takes two people. One person pushing and sliding the plywood up the ladder and the other person pulling on the rope while on the roof. It actually goes pretty easy. My RV has a fiberglass roof and I'm not small....weight was no issue!
