Here's how I ran the wires from trunk to dash:
With the back seats folded down, you can see the hole where the wires run:
Then, with the back seat out, you can lift up on the shoulder padding part and pull the cable through:
From there you can run the cables where the others run in the door jam:
Then I took out the front driver's seat (tip: the tire iron in your car's toolkit is the right size to loosen/tighten the nuts holding the seat in place), and ran the cables underneath it (following the crease already in the carpeting), and ran the cables into the center console/armrest, underneath the gear shift, and up to the dash where the monitor sits.
The hardest part was getting the plastic cover off of the door jam that exposes the end of the carpet so you can pull it back and run the cables. You really have to pull up hard on it, and I had to replace some of the white clips that hold it on, but they're really inexpensive.