You may (or may not) want to read this thread detailing with my experience with my wife's 2006 E350 wagon and its transmission. Note ILUVMILS's post closer to the end where he points out that it is possible to change just the conductor plate on the 722.9 in some cases. Not sure whether this is still a "dealer only" repair...

http://www.peachparts.com/shopforum/tech-help/307933-06-e350-722-9-transmission-sticks-1st.html

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Christopher
'06 Mercedes E350 station wagon (silver/black)
'85 Mercedes 300D (black pearl/palomino)
'85 Mercedes 300SD (smoke silver/burgundy)
'79 Cadillac Sedan DeVille

'05 Toyota Camry (because always running is nice)

'85 Mercedes 300D sold back to orig. owner 8-1-06
'84 Volvo 264GL Diesel, owned 2000-2013