that RVcam site could possibly be one of THE most expensive (generic equipment) solutions on the internet. ALL of this stuff can be sourced via amazon (or even cheaper).
I recently saw some 7 inch monitors for pennies (buy an extra and you're STILL ahead of the game).
$27.95 - 7" (2 channel) MonitorTurn any (wired cam) into wireless with this 19 dollar converter -
HEREthere are all kinds of cable conversions to go back and forth between DIN/Pin, BNC & RCA with 12vdc (to power the camera), I cant find the link but i used one myself.