Fortunately, I've had very little go wrong so far on the road or in CGs. And I haven't had the opportunity to help anyone else, either.
My Dad did help me solve an electrical problem once. DW, daughter and I left Asheville, NC towing our then popup. It was cold and rainy, raining on almost the whole trip to Charleston, SC New Year's weekend. When we got to the CG, we raised the roof to find everything dripping with water. I first thought the roof seal had leaked horribly, until I realized even the bottoms of all surfaces were wet. Condensation. Warmer, humid Charleston air hitting those cold surfaces.
It shorted out one of the receptacles, so the GFCI kept tripping. Dad helped me trace it to the outlet in the fridge compartment, which we dried out with a hair dryer. Problem fixed.