The ONLY way to do this is to remove the tranny. It is really easy to get out if you have the specail tools...I have the ones needed and can pull the tranny easily.
I have NEVER pulled an engine for such a job.
You are right in the assumption that the tranny R&R is most of the labor. Also, with the tranny out, it is a good time to replace the transmission front pump seal. They all leak eventually.
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MERCEDES SPECIALIST 11 YRS