Pretty straight forward. DIY job yes.
I just popped off the cover piece with a wedge tool. The connector as shown in the picture has 3 wires -- Red, yellow, black. I suggest to use a multi meter to probe. I don't recall exactly which I used. I think theres another thread on here where someone had pictures of exactly which wires he tapped.
I did have an issue initially when I hooked it up I wasn't getting power. Took me a while to troubleshoot swapping the mirror taps, radar detectors, etc... between my other car. In the end it turns out I had a blown fuse which Tesla replaced free of charge. They think it was due to my blackvue dash cam from the installer? Just a FYI.
Just be careful when sticking the wire tap into the connector. It's very snug and can break if you apply too much force.