Supercab79, in my rig, there was wiring. I didn't order it that way. I had my fingers crossed the whole time I was unscrewing the 4 screws that hold the interior trim piece in place. As soon as it was loose, I could see the wiring peeking out of a hole.
Helmsey, this was a huge chore, but maybe I can help anyone else who wants to do it. This is from a 365SAQ model, which I see you have as well. In the bunkhouse, in the closets on the top shelf there's a wooden wrap that goes around. Remove that, and that is the location I ran the wire into. Then (I used the passenger side) remove the wooden side panel on the interior side of the closet. I removed the screws and the side panel was stapled along the front, I worked it back and fourth carefully until the staples pulled through the back side and didn't hurt the wood (when putting it back, it fit so snug I haven't even re-stapled it yet). You run the wire from the top to the middle section and then remove the side panel on the very bottom. The pipe actually runs at a diagonal to the right of the TV in the bunk house. The side pulls out very easy as well. I used a wire fish rod to get the wire moved down to the bottom. Getting it outside was a B*&ch. I tore as much of the spray foam from around the pipe entering the floor as I could. I then used two people, I was outside just behind the bumper and was able to squeeze my fingers between the bottom underside of the trailer and where the "roll" of the enclosed belly starts at an area I figured was dang close to that pipe. Amazingly, I found the pipe rather quickly and with a guy inside we worked the wire until I was able to hook it with a standard fish tape and pull it out. Once out I wrapped my wire with 1/4 split loom and zip tied it to anything I could getting it to the front of the camper. I took it in through the driver's side propane cabinet, drilled a hole into the interior cabinet and brought it inside the middle. Then took out a few screws from the underside of the fifth wheel to let it loose slightly, I didn't pull any caulking or trim. Inside that middle cabinet on way at the top I used a pry bar and gently pushed the wood trim apart from the metal. Using the wire fishing rod again I sent the rod out to the pinbox and pulled the wire through. Like I said, this was a huge undertaking, but I wanted it to look super clean. At the pinbox I converted my camera to a standard trailer 4 pin so I can unhook it easily.
The camera I bought was this one in white, and from ebay to save $$ Super CMOS Color Rear Mount Observation Camera
The screen I am using is my head unit so I can have it on whenever I want by simply choosing the A/V input.
They make a nice connector for the camera, but my budget didn't want to take this big of a hit. Voyager Bulk Head Camera Connector
It cost me roughly 25 bucks to wire it my way.
I hope this makes some sense. I can take pics if you need them. I really liked the idea of adding some teardrop camera to each side as well, but the AV switch box to select which of the 3 camera is showing is quite pricey so I thought I would start with the back-up camera and go from there.
Speaking of back-up camera... I have trouble hitching up. My hitch sits just low enough in my bed and I have a tonneau cover that when rolled up to the back window blocks my view completely. I added a back-up camera just below the 3rd brace light that shows me my hitch. It integrates with my rear view mirror and the factory camera shows up on my navi screen where the camper back-up camera also shows. All in all, I'm super pleased.