So after a significant amount of studying the manual and recruiting the wife to help me remove the trim strip, we got it removed without breaking what feels like fragile plastic. Minor miracle. Getting to the back of the fridge was easy from there. We found it clean with abundant space for air flow, but a fan that just would not start. It ran once I flicked it, but every time the compressor cycles it would fail to restart. A new 120 mm fan and it's ice cold inside again.
I can see how additional insulation would help, but the fridge cabinet is well inside the salon on the Mariner 37 and as good as I can imagine. When it comes to saving watts, I think there are bigger fish to fry on our boat. Additional insulation will have to wait. Thanks all for your help on this. And Barrie, patience is what it took. Thank you.