I would say NO. RV dealers don't understand the structural issues involved with the boat. They don't know how to seal the core with epoxy. They often use wire nuts, instead of a proper marine crimp fitting--see below ref wire type.
It is a bit more than just cutting the hole. Although, you can cut the 14" square hole, I do believe it best to square up the top--at the very least, so that the gasket has a level surface to compress on. RV's have a fairly level roof, with less crown than the C Dory.
Here is a photo of the top strengthened and faired level for the upper gasket of the RV AC unit on the Tom Cat 255. We laid strips of glass cloth and epoxy to build that surface.
The underside, wood cut to the contour of the underside of cabin roof, for the air handler athwartship pieces clamped and epoxy glued in place:
The final product inside, before air handler installed:
The boat should already have 120 V AC power installed and a separate breaker for the air conditioner. The wiring is usually run up the inside by the aft dinette seat, or can be run from up forward along one side of the window pillars. One should not use Romex house wiring, but 12 gauge tinned copper marine wire (3 conductors, neutral, hot and ground).
Get a marine contractor who understands the marine requirements.