Had replaced the oil level sending washers a few years back, so they were good. Used RTV Copper the first time, very thin, and never got a good seal. (in fairness, my ex-wife hit a barrier a few days later, big dent in pan and leaked forevermore) This time, i replaced the pan and sealed the new gasket with (common brand name, not coming to me now) HPF which stands for High Performance Formula. No drips, no runs, no errors. Did the pan a few weeks after finishing chain, rails, head gaskets. Lots of residual "crumbs" in the pan.
Cigar--if You found a bit of rail, have you checked your rails? When my upper left one broke, it also broke a lower rail (found a piece in the oil pan and it had the part number on it which i referenced through FastLane. Closely inspect the piece You found.
Emmy--it's a fairly straight forward job, but don't overtighten the bolts. i think the torque spec on my 560 was only 5 or 6nm, pretty light. i probably am closer to the 10 that Cigar used, but did it by feel.

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Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)