I went with RV Cams, but as for the monitor ... My 7" monitor came with a puck mount (1 screw) that I mounted to a metal brace under the headliner between my sun visors. I dropped my dome light assy down and tapped power from it running a fused wire to the monitor. Nothing shows, no messing with a dash mount, and is easy to glance up between the sun visors.
we have had the RV cam unit since 2006 with not a problem. Being lazy we mounted the cam on the top rung of the ladder under the RV on the underbelly then up through the front of the RV out of the hitch. The monitor is dash mounted. The cam is something we would not be on the road without.