Peter,

In trying to prepare for the worst, I have called all the indies in Nashville and found out none of the major players rebuild trannies; all replace them. I am working on the theory that a shop capable, qualified and willing to rebuild a box might identify a problem that does not require a rebuild. It would intuitively seem less likely a 'we replace transmissions' shop would identify such a fault.

Expanding the search and by accident, I called a wholesale trans parts place who told me they thought one of their customers solely worked on Mercedes transmissions. They gave me his number.

I talked to Henry, who told me he only worked on Mercedes transmissions. I described the symptoms, and his first speculation was that it could be a servo leak.

My battle plan is as follows;
Tomorrow I will remove the excess fluid, clean the case, and hose it down with foot powder. If I can get it to shift in the first couple of 100 yards, I will take it onto the highway to get it into 4th gear.

If it will not shift in the first couple of hundred yards, I think I will have it towed to Henry and let him deal with it.

I don't know whether to be worried or elated... I asked him in a worst case scenario what he got for a rebuild.
The answer was $1000 including the kit.

However, when Nashville Transmission Parts tells me he buys more Mercedes parts than anyone else it sure seems to lend credibility...