The screws around the perimeter of the gauge cluster hold it in place. Ditto the switch panel. Ditto the trim tab switch. There is plenty of room back there, but not a lot of extra wire. There is enough to get it out of the way. They did a far better job than most in that arena.
I looked at that setup. Before you tear into the dash, check the placement parameters. When I looked at this 5 years ago, the recommended location was as close to midships as possible which would put it somewhere in the aft cabin. A lot has changed in microchip technology in 5 years though.
Maybe Tabman will chime in.
BTW, depending on your engine and that Navman unit, you may be able to get diagnostic information from the engine sent to that screen.