I pulled the balancer on both my 300D's. On the 1982 engine (in my 1985), the 2 pins stayed on the balancer. Indeed, I thought they were integral with it. It went back on w/ no issue (after changing the crank seal). I wasn't so lucky later w/ my 1984 and then figured out "how it works" (should have read the FSM). I found you aren't supposed to re-use the pins, and they are fairly cheap on PP. But some have reported new ones are need trimming (your old ones?). Also, they are not 180 deg apart, which sets the damper clocking to the crank. Punch mark the 2 before removal. I did, but then found someone had placed earlier punches and confused with mine. I was working w/ engine in car, so had to use a mirror to view, which made it much harder. Anyway, after several attempts I finally got the damper back on the 1984. Be careful or you could destroy your crankshaft.

The damper didn't pull off easy on either car, but wasn't too hard w/ a rugged "pulley puller" (Harbor Freight). There is a wiki on installing the new crank seal. You must fold the lip up over the crank ring. I must have lucked out on the 1982 engine, since I don't recall doing anything special. On my 1984 engine I tore the lip of the seal and had to try again.

In earlier post on your rear crank seal, check if you need sealant between the metal-metal gap of the bearing block and engine. In some engines, you need a thin anaerobic like Loctite. I haven't done my M-B engines.

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