Baja Man wrote:
Does that mean that the marker lamps have a continuously hot wire or a wire that has 12V power all of the time?
No.
The camera will get power anytime the parking or headlights are ON, so you can select whether it's on or not in the day time. Then the receiver can be ON or OFF too. Of course both must be ON for it to work.
As was said, mount it close to one of the red marker lights, below or beside, and make an extra hole in the base of the marker shell or in the siding immediately beside it.
Calking/sealant made for an RV roof is probably best to finish the job.
P.S. I don't trust glue OR screws by themselves and I use BOTH when mounting something like that.