The way I've seen it done is to cut holes at the front corners around floor level, fish a heavy chain/cable through and then drag the cable down the length to get the walls detached from the floor. For a class A you would obviously want to pull the motor/trans and anything of value from the cab before doing this. Where I'm from the cable is typically strung between trees and the trailer is towed or the cable is strung to one tree and rotated in an arc about the tree by a truck/tractor but you don't have trees in the desert so you'll have to figure something out.
Once the walls, interior and roof are removed from the body and on the ground it's easy.