Best to remove the oil pan to do this. I fussed with the old hardened rubber grommet from above on my 1985 300D for over an hour. I removed the pan on my 1984 300D to do it, which allowed easily tapping the old rubber up and out from below, using a socket. It is tricky working the 2 drain tubes off and back on. You must orient them just right and against the block to get just enough room. There is an O-ring between the 2 tubes which needs changing. I used green HBNR as I recall. If cracked, you will loose a lot of oil since the "funnel" is upside-down. Also use a new gasket at the turbo drain flange, and clean the old one off well. It probably helped that I re-routed the high-pressure AC hose directly to the condenser, rather than the crazy "up right side of block" the factory did. That gets that bracket out of the way to easier get at the top of the drain stub, and also makes it much easier to get at the alternator bolts in the future.

Good that I removed the lower oil pan since I found a bolt sitting in the bottom, which mounts the oil pump, and found the plastic spring-loaded tensioner cocked and jammed as its pivot hole cracked. People say that you must remove the upper oil pan to remove the oil pump and change that tensioner, but not true. If clever, you can get the pulley off with the upper oil pan in place (I did).

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans