Jim,
In our current (& previous) 5th wheel we had the existing over-head bedroom vent replaced with a 12-volt fan. Dealership did the job as part of the sales agreement, so I can't help much with specifics, but I do know --
Previous FW was 50 amp (wired for 2nd a/c) and our Laredo is 30 amp. Each time, power for the fan (2 different brands) was accessed at a nearby 12-volt light. Obviously the service tech's are more familiar with the wiring, but 2 different dealers/tech's and they were each done in no time - which gives the impression that it wasn't a tedious task! No disrespect intended toward the service tech's, of course!
Hope this helps... at least a little,
Terri, the Chevy co-pilot [& DH Kevin]