A sudden complete stoppage of a 3-way fridge does suggest a DC issue. A 3-way fridge that suddenly begins cooling very little suggests other than a DC issue. So the first question is, have you verified that it is TOTALLY dead?
There is a circuit board in the front part of your Dometic 2351 (that's what it is from the pic I see). Sometimes those fail. I've got a blog post here
which describes how we did an early board replacement (which ended up NOT solving our problem, but there it is as food for thought).
'Tis the season for fridge failures. There's also the issue of what to try if the fridge is operating but not lowering the temperature very much. See this other thread here
for information on that scenario.