Here's a write up with some pics. This is the process I went through to route the satellite antenna wire in my '05 CC: (I will refer to previous pics/steps as I go)
1 -- 1/4 drive ratchet
1 -- short 1/4 extention
1 -- 1/4 drive 8mm deep socket
2 -- small zip ties
1~5 -- alcohol prep pads, or some rubbing alcohol and a clean cloth
Step 1: Yes, it may seem silly, but it all begins with removing these.
Once removed, you'll see this.
(this photo will be reused later)
Locate the stud coming from the 3rd brake/cargo light and remove the nut from the stud.
Step 2: Once the nuts are off of the 3rd brake/cargo light, you may find it necessary to push on the studs with something to get the light to separate from the truck. Now, it's time to locate the antenna on the roof of the truck. I went toward the center, but I only eyeballed things.
Once the antenna was near where I wanted it, I fished the end that goes to the radio through the hole that you will see with the 3rd brake/cargo light removed, and into the hole in the headliner so that I could find it inside the truck. Feed it all into the cab, no need to leave excess at this time.
This is a close up of where the wire for the antenna actually goes behind the 3rd brake/cargo light into the cab.
I don't think there will be a leakage issue as upon inspection, the rubber seal of the 3rd brake/cargo light appears to form around the antenna wire well. (If a leak is found, I will probably just put a small gob of clear silicone over the area.)
Step 3: My antenna had a "guard" that goes over the wire that also has two sided tape on it. I cleaned the roof of the truck with alcohol pads to prepare the surface. Put the guard on, double checked my placement, then peeled the tape. At this point, the outside work is pretty much done. Go ahead and put the studs of the 3rd brake/cargo light back where they go.
Step 4: Go inside the truck and find your wires.
This is an important part, because if you forget this, you'll have everything run and then have to start over. At this point you should have a gob of wire coming out of the hole shown after you removed the caps in the headliner. Find the end of your antenna wire, and take it back to the hole. You'll need to push the headliner down slightly and feed the end of the antenna wire between the rear glass and the headliner. Pull the majority of your wire back between the headliner and the rear glass.
Once this is done, I tossed the end of my antenna wire into the front seat and went there to begin the feeding process. I fed from front to rear so that all of my excess wire would be in the back of the vehicle.
Begin by simply pushing some of the wire between the dash and front glass. Follow this process until you reach the passenger's side A pillar. Make sure you get the wire into the corner so that you can get it behind the A pillar. Feed it behind the A pillar until you reach the headliner.
Once the headliner is reached, just stuff it between the headliner and the door seal.
Follow this process until you reach the B? pillar. Get in back seat and follow it to rear corner of the truck.
Keep tucking, cramming, and poking the wire as you go. Once you get to the rear corner, you can pull your excess back through the hole in the headliner. Cram the last little bit between the rear glass and the head liner, then use the zip ties to neaten up all the excess wires.
Put the excess wires into the headliner hole.
Step 5: Replace the bolts on your 3rd brake/cargo light and tighten. Be careful not to twist the studs off. (Why I chose 1/4 drive) Put the caps back in the headliner. Finished!!