Thanks for the input M60. It looks like the lighter problem is internal . The socket inner contacts/lighter holder appear to be bent up and contacting the case around it. I assume that creates a dead short. I have watched videos on getting the unit out of the dash, but nobody so far has shown how the lighter socket is then removed from it's location. If it is unrepairable, I'm thinking new ones will be hard to come by.
I think I will drive the car to an auto parts store and have the codes read. I have a newer Harbor freight reader but it doesn't get very far into Mercedes modules. I'm not real sure auto parts stores will get very far either. But, worth a try. Still more to do!