Can't help with a vendor but the actual replacement isn't much different than on most any Aquasport. The stringer system ties directly into the transom face and the "cap" attaches to the transom at the motor well cutout. They covered that connection with a plastic cover. The operation is a little more difficult because of the rear storage (battery/oil) compartments on each side that you need to work around. While I never did my 91, I have often contemplated how and several areas would need some trimming for removal to allow full access to the transom.
I would pour but you might save a little cash (?) with a wood/composite and glass replacement.
You'll find wood in the deck, the gunnel tops and the cabin used as coring. You may also find it in the tank compartment used as support for the tank itself.
Good luck.
