DV seals a super easy with the special socket and a torque wrench. As for the oil leaks... I had some oil coming out mine from the driver side. Looks like a square plate with a few flat head screws. Tightened each screw a bit. Seems to have stopped most of the leaking.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"