I imagine it is fiberglass. Have you ever performed any fiberglass work? I just did some work on a tractor canopy and it didn't turn out to bad. I started with some fiberglass that contained "kitty hair" (tiny strands of fiberglass) and have sanded it down. I still need to put a gel coat on the top and then paint.
A local automotive paint store such as KOI will have the materials.
Steve, Christy, Anna and Phoebe (Border Collie)
1994 Classic 30'11" Excella - rear twin
2009 Dodge 2500, 6 Speed Auto, CTD, Quad Cab, Short Bed
Hensley Arrow hitch with adjustable stinger
WBCCI # 3072