Hooking Up Camper Shell Wiring? How?

[Xtrema]

Although this is not towing per se, I thought you experts might be able to help me with a Leer camper shell wiring opportunity. The shell has a flat-four connector to get dome lights and high center brake indicator lamp going. It is on the driver's side, and looks like they expect it to reach the driver's taillight.

From some posts, it seems that there could be a connector behind the driver's taillight. But, with the official trailer towing package already on the truck, is it already in use?

And, of course, I can remove the bolts holding the taillight in but can't figure out how to get the light out of the fender. It feels like there are tabs of plastic on the forward edge of the light and I do NOT want to break them!

Thanks in advance for your able assistance.