I don’t know anything about the Pleasure Way but I know a little about the Chevy 3500.
The wiring comes from the front, goes up the drivers side rear door post and crosses the top for the passenger side tail lights. On the Roadtrek the upholstery has to come off to give you access to the door post wiring. You could look underneath and see if you can access it from beneath. I could not. Roadtrek placed a Curt electronic module in there that had inputs of the OEM wiring and outputs for four wire trailer wiring.
You can start here:
https://www.curtmfg.com/all-products...t/express_3500
It appears you already have it.
The fuses are underneath the driver’s seat which is another issue. On the Roadtrek the seat may have to be removed to get the fuse block cover off. Better to not blow any fuses.