DHill57,
The Jensen and Garmin systems will not interoperate. In each system, their cameras are matched/paired to the receivers built-into the monitors.
I can appreciate the likely reason you have for wanting to use the Garmin GPS with the Jensen camera (a single monitor solution for both backup camera and GPS receiver). I will say that I have had both systems and since I don't need a GPS, I prefer the Jensen system.
That said, if I was in the market for a new large screen GPS for navigations, using the Garmin backup camera / GPS system makes a lot of sense.
If you were to change over to the Garmin system, you'd need only get some 12 volt power to the rear cap. I'd use power from the rear cap reading lights. The Garmin system comes with a transmitter that mounts near the camera. Heartland mounts it in the upper cabinet. I'd install a switch in the DC line so you can cut power off to the system when you are setup at a CG for long periods.
Note that v1 of the Garmin system has no audio or LEDs on the camera. I believe they are working to add more features to v2 product.