I think/hope that I know where the wires are for the speakers. Given that folks have said that I should have access through the stereo, and I looked a YouTube video that seems to show an "optional" stereo in a 2007 Puma 19FS. My camper apparently was purchased without the stereo option. I am going to cut into the cabinetry and hope I find a 12volt power wiring harness for essentially a car stereo. Fingers crossed...
2007 Puma 19FS
2012 Silverado 1500