found this link from someone's post when I searched the letters "QDIS."
There is a youtube link as part of the post -- looks like the X6 who retrofitted the system did NOT have NAV, the screen looks smaller than the the ones I have in mine. So hopefully this will help answer those where did not have NAV.
Besides reverse camera, looks like the "media box" (you'd have to mount it somewhere) can allow 3 other RCA input (DVD player for the front screen, or night vision camer in the front as it was OP described)
I look forward to add this feature to mine if the instruction is not to complicated -- looks like that also mentioned there is a "pre-existing" hole for the camera instaed of being part of the hatch handle.
VIDEO of my Retrofitted rearview camera - XBimmers.com | BMW X6 Forum X5 X3 Forum