As soon as I saw "5 speed 4matic" I knew it had to be a Euro. Many 4matic owners in the US have wished for the 5 speed, but I like the slushbox just fine for the family car. If you want a sports car, don't buy a 4matic.
I still think you should find a dealer that has experience in the diagnosis and repair of 4matics, even if you have to drive a little to find one. There are so many inputs to the 4matic computer that can cause trouble codes, you'll go broke doing the "throw parts at it" approach. You may have even toasted the control unit, who knows with the electrical transients you have described.
I don't think you'll do any more harm to the system driving it if it isn't binding or giving you any trouble on the road. You can always shift the test valve under the hood to test position just to be safe. That isolates the hydraulics from the rear of the car.