I had to shorten a shaft after putting a 4-sp in. It cost me under $200 (wholesale possibly), similar price on a similar job on a Grand Wagoneer years ago. Check your Mercedes specialists; a few guys I checked with first said they would not touch it, or said it could not be done. I found out who the dealers used.

The place I used did limos and trucks. Good job; no issues afterwards.

I would keep looking. Find someone who sounds totally confident.

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K