Alan-
Fix what you have.
Winnebago supplies online wiring diagrams for your coach
here. Your coach came from the factory with a 6-pin hitch connector, not a 7-pin.
Ford provides fuse panel information for your coach online,
here. For starters, check fuses 5 and 6 in the Power Distribution Box (see page 130 of the manual). The PDB is under the hood- I'm thinking on the driver's side, near the front.
It appears as if the rear lights on the coach and the trailer lights were spliced together at the factory, so the logical question is: "Do the lights work on the coach?"
The next question is: "Is the ground pin connected to ground?"
And finally, "Are there any odd-looking wiring or components within four feet of the hitch connector?"