I went with a Rear View Saftey camera kit (RVS-770613).
It cost me ~$200 from Amazon.
I've been using it for a few months now and really like it.
The picture quality is pretty decent. It's color. Camera has IR for night viewing and a mic.
It has multiple inputs (3) for additional cameras.
Comes complete with everything needed to install it.
Has a remote control - I guess to turn it on while sitting in your easy-chair and hear a noise outside, lol.
The overall build quality looks pretty good.
The parts and cables appear to be of high quality components that attach and seal well.
I will say that all of the wires can be a pain to manage and tuck out of the way.
Plus the cable-head you need to run inside your rig is ridiculously large. It does make for a nice solid connection, but requires a large-ish hole to poke it through. Fortunately for me the old camera installation already had a sufficiently large hole drilled in the roof.
While I considered a wireless system, I pretty quickly dismissed it. Wireless is already a PITA to get into and out of that bus, and I figured this wasn't going to be any better trying to send a relatively weak wireless signal through 35' of an aluminum faraday-cage.