I just pulled like a neanderthal until the clips released. you pinch the little plastic piece around the rearview mirror first, and it can be a real pain to remove. Once that is off, you can twist the entire mirror assembly (i forget which direction) to detach it from the windshield. Once you have those off it is a bit easier to pry the cover off. As always, just go slow and listen for clips detaching.
sorry i can't be more help - i'm not anywhere near the car today.
Edit: and i just used a multimeter to find the thing I wanted to tap. word of caution - there is a 12v that looks like it might be useful, but powers the small cooling fan for the cameras, so avoid disconnecting that one.