no nav right? because if you have nav, if im not mistaken the image comes up there. I know wires will be going to the mirror for the auto dimming feature. i guess it would all depend on what wires were going to the mirror, if the mirror actually had the screen in it.
also, if you open the tailgate, is there any wires running up through the bottom? i dont have a picture but in my truck there are wires that run from the truck to a connector thats at the bottom of the tailgate, then theres wires in the gate plus the handle and the camera. So i think i would crawl under or take the tailgate off first and see if there are any connectors without a connection, if that makes sense, that reach the tailgate.
I would assume everything like that is prewired as to not have to many wiring harnesses in the production process, because i know the dash harness in my truck has all the plugs for accessories i dont have, (auto 4x4, parking sensors etc).