Made more good progress today. Got all the old ceiling insulation taken out. Luckily I didn't have to mess with any of that sticky black tar stuff. Mine seemed to be held in by a spray adhesive and using a long bladed putty knife I was able to get out all the residue pretty easily.
Also took out the first side panel. That did not go as easily. The very top of the panel is slid under the bottom of the window frame. So I tried taking out two windows and wouldn't you know it, the damn things we tack welded to the frame where they slide under the window. So I had to use the angle grinder and cut the top of the panel across right under the window frames. At least now I know what lies in store for getting the rest of them out.