Aluminum Frame Construction

I have a 2004 Fleetwood Wildernes Advantage 5th wheel. It has aluminum frame construction and what appears to be bonded fiberglass (or something) exterior walls.I had a rear roof to wall leak that has caused delamination visble from the interior. Is the rear framing aluminum or just the sides. If the rear is aluminum, I hope to repair the laminate damage from the inside. Any construction details and references would be appreciated. Thx.
Mike in Maine