By the way you put that together in words made my body hurt just reading it, I don't think I could even attempt a job so to say with out any kind of pain. LOL..
Nope, the access is through one of the storage doors above that one, then there is a little square wooden box between the risers from the sub floor to the deck, right against the gas tank, they are wooden risers, 1/2 plywood, about a 1ft wide, 2ft tall, that support the upper deck from the subfloor that the gas tank set's on, right under the windshield, the little door in the middle, at for feet, is the ski locker, it's 8ft long.
It's is a universal type wiper motor, not specific to the boats. The motor is kinda hard to get to, but something I done to the gold boat was spaced the motor down with a bushing so it didn't stick up so high on the deck.
Any parts store can get in their catalogue and come up with one I'm sure.