A guy named Clark Grigsby used to work on my 6.9 in Houston. He moved to Georgetown and worked for a Porsche shop and now I hear he is on his own. Don't know much more than that but he knows MB cars like nobodys business. You might see if you can look him up.
A lot of shops all across Texas send their trannies to a guy named Jurgen in Houston. He does not work for the public, but for repair shops, in other words he doesn't pull the trannies out of cars.
http://www.jie.com/
I talked to him once and he is very helpful, he might be able to give you better insight into your problem.