I thought the original $650 price was pretty fair, I wouldn't want to do the job without taking the headliner out, and to take the headliner out all of the seats and pillar trim have to come out. It could be a few hours labor easily. I just had the front of the headliner down to put some silicone around my XM antenna and add the dr harness auto dimming mirror harness in and it was pretty tough to reach in there.
That would make be a bit nervous, those are made to punch holes in electrical boxes. Greenlee make a lot of electrician tools. The fact that the roof isn't flat, I would worry about putting a crease in it. But the picture seemed to work well.
The marker lights come on automatically, the switch is something wired so you can put on a beacon or a strobe for the plow guys.