Brian and Vicki,
I saw your post on another thread, and see that you have a '99 (I think it was). On ours, it peals off easily (ours was damaged at time of pick up and is scheduled to be replaced by WRV. When I took it to a place to have it looked at they were able to easily pull back a corner) but ours is new and I assume that with age yours has hardened and become brittle peeling off in "1 inch squares" I dont know for sure about the 3M, but with vinyl decals I was able to remove that with what looked and felt like a large "art gum" eraser type wheel that I purchased at a local auto paint store. They said that they use it for removing decal pin striping on cars and it worked well (with a lot of work) taking off vinyl decals on my old motorhome. Hope this is of some help. Again, I dont know how well it would work on the 3M.
Hugh & Cyndi Reed
35' 2004 Damon Intruder 2 slide
2004 Honda Element toad