See if there is an O-ring on top of the existing one, its inside a channel in the cannister that has a long bolt running thru it, the PO might have stacked the O-ring ontop the old one in the channel and that will DEFINITELY cause what you described, oil all over the ground.
I hope the engine survived (any new unusual noises?).

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!