I recently had the good fortune of picking up a nice original Day/Night interior rearview mirror. I was wondering if this was a special dealer option or part of the interior decor group. Also, will it require any special or additional parts to attach to the current setup or is it just a simple swap out with the current mirror? Final question - it has that knob on the bottom that rotates. Just wondering how this is supposed to function in regards to the day/night feature. Thanks.