for what it's worth....
I installed two wired cameras - one at the back and one on a "roll bar" made of pvc on the truck.
I bought two cameras, wiring, and monitor from ebay.
I bought some small pvc conduit and ran it under the trailer - it's flexible so I went over & under a few things and secured it with cable ties. I secured the cable to the front of the the fifth wheel & up the hitch area with small self adhesive cable ties. When disconnected from the truch, the cable stores uo in the back of the hitch with the brake cable.
Initial plan was to have a connector in the bed of the truck & use that for switching. I decided to leave that in the truck and bring the camera lead in the back window when needed.
The display was a rear view mirror mount/replacement - it's mirrored so you can see either normal mirror or display. The wiring up to the morror ran along the column and top of the windshield wedged under existing trim. Easy.
The trunk mounted camera is great for hooking up - with it I can see both the hitch and the pin.
The rear view was an interesting novelty at first - being able to see cars directly behind me. Not of much utility in backing up because I have a navigator/ground guide. I don't even hook it up any more. If I ever find myself traveling alone I'm sure it would be more useful.
My rear view mirror is glued to the windshield. With the extra weight of the monitor, it fell off after several months. Re glued by the dealer. Fortunately there is a connector right at the monitor so I put it in place for hookup and then put it away until next hookup.
Joel