I am waiting for the hotwire kit to come in the mail from Valentine. I always use the sunroof wire to connect, then use the visor clip - I've done this in 4+ cars and it should be pretty straight forward. The overhead panel usually just pops out pretty easily. I used it with the cord running from the cigarette lighter outlet for the 500 mile trip back from performance center and didn't notice any issues with it picking up radar, but I guess the only way to find out for sure is to try it next to another car that def has no issues.
That's the first I've heard of any interference with the windshield hindering performance.