Search threads for this. There are lots of write-ups out there. I remember reading several when doing my setup on my old van a few years ago. I'm about to do it again and will pass on what I find out. I'm currently considering a Boyo 5" wired monitor, which hopefully reverses the image since it is marketed as a backup camera. I'm unsure on the camera though. I had a GREAT field of view and overall performance out of my Boyo license plate style camera, which I mounted up top. It looked funny up there but worked great. Still, I can't decide if I want to put one up there like that again or go for something different.
Boyo stuff is pretty affordable and available on Amazon and is a solid brand.