So I found that our local repair station could handle the finishing. I demoed out the unwanted items and expect to get the unit back this week from finishing. Orig. wall paneling no longer available from Keystone, generic white ceiling panel and batts are. I did find corner trim, batts and tape in orig. color from RV Parts Nation. They have wall panels as well, but freight prohibitive.
The opening up of our unit completely transformed it. MUCH more useable, seems lots bigger.
We addressed a structural issue by shortening an aluminum framed wall to 8" to act as a truss across the top of the garage front, anchored at the wall where the slide terminates just in case she wanted to rack a bit. Next up - plank flooring.