For installing the dashcam, I largely followed the method here, except I used a USB to Mini-USB cable, with a USB power adapter in the 12V socket:
First step was to attach the camera to the windshield with the included double-sided tape, and I made the mistake of putting it on the passenger side. I thought that would prevent it from blocking my view, but it also meant the SD card slot is very hard to reach, as the mirror gets in the way. I had to use a pen to push the card in and out, and ejected it across the car a couple of times. Hence, the best solution was to leave it in permanently, and use the USB cable to copy videos off to my laptop on the few occasions when I need to download one.
Next step was to remove the cover over the windshield pillar. As mentioned in the linked post, you can just grab it in the middle and carefully pull it away. It’s attached more solidly at the bottom, but can be pulled out. Then it hangs from the pillar by a plastic cable, and I just moved it aside rather than disconnect that.
That done, I used a piece of plastic to push the cable into the roof of the car–there’s a hole behind the mirror which is just about the right size for the cable to go through–and along until it reached the pillar. Then dropped it down the hole between the speaker and pillar, and pulled it out into the passenger footwell through one of the holes at the bottom.
About half the pillar is taken up by the side curtain airbag, and I didn’t want to risk having the cable interfere with that if it went off. So I used cable ties to attach it to the existing wiring that runs down the pillar. I managed to drop one of the cable ties and it fell down behind the airbag, but fortunately, after I poked it a couple of times, it fell down further until I was able to pull it out.
To reattach the cover, just push it back in at the bottom, then push the sides back into the pillar. Just be careful that the sides go inside the weather stripping on the door frame and not outside. I got a couple of inches at the bottom outside the weather stripping, and had to pull it out again.
I used the cable clips which came with the camera to run the cable across beneath the glove box, but that’s not really ideal, since there’s not much clearance for passengers’ feet, and they could easily kick it away. I think I’ll have to tape it up.
Then I ended up with about six inches of the ten foot cable left over to plug into the power socket. Just about enough to comfortably plug it into the laptop when I need to.
After that, all I had left to do was attach the cable cover. The base was already stuck to the windshield, but the cover was difficult to fit as I’d left too much slack in the cable to the camera, and had to carefully push it in until the cover would actually fit. Since I don’t plan to detach the camera at any point, I should have only left enough cable up there to reach it, and the cover would have fit more easily.