I actually didn't go through the OEM rubbet boot to the tailgate. I just left a small "slack loop" to mimic the movement of the factory boot.
Once you remove the inside liner and assist strap (Torx bit), you have to peel back the vapor barrier to access the 4 nuts that hold the chrome lic plate lights bezel in place. A long extenstion bar makes removing these so much easier.
There are several options for running the power and video cables.
I ran mine above the headliner. Get a good electrical fish tape and it's not a tough job. I did remove the light over the rear seat (driver's side) and the center roof console (abover rear view mirror). Since I have the rear A/C ducts in the ceiling of my Ex, it took a little finesse to get the fish tape by the duct work.
I then ran the cables down the passenger side A pillar through the glove box and over to the head unit. You'll have to remove the grab handle on the A pillar to remove the cover. Be advised that I have an airbag in my a-pillar so I had to be careaful as to the route for the cable not to interfere (sp) with the possible deployment of the airbag.
I also ran the control and power cables for my rear emergency lighting the same route as the camera cables.
As I have already written, I did not tie my camera into the reverse circuit of the truck. I installed a toggle switch in the audio in jack to turn operate the camera. This way I can use the camer whenever I choose, not just in reverse.
Hope this helps with you installation.
Marc
