What are the symptoms, and what codes is it throwing?
It is my understanding that with the 722.9, the valve body often needs replacement, as opposed to just the conductor plate, which is a common repair on the 5-speed. For a while MB was having to repair so many of these that the valve body was only available at the dealer, and even then there was sometimes a wait. However, at the end of this post, the OP suggests there is some sort of "kit" now available at MB for the repair:
http://www.peachparts.com/shopforum/tech-help/341096-2006-e350-stuck-gear.html
At any rate, I agree with engatwork, I'd probably just take it to the dealer...