Welcome to the Forum - you have discovered a great source for information. As for your question, if you had oil in the coolant, I would say you have a blown head gasket. But coolant in the oil usually indicates, as Larry said, a cracked block. The pressure in the system is such that with a blown head gasket coolant cannot flow into the oil, but rather, the oil flows into the coolant. I strongly suggest you do a search here on this subject -you will find a lot of useful information.
Do you have the complete service records for the car? If the head gasket was never replaced, (unlikley since this was the achilles heel of this engine), or you are unsure, but there is residue of oil in the coolant, then it means one of two things: either the gasket is blown and needs to be replaced, or the oil is residue that was not properly cleaned from the engine after the gasket was last replaced. The only good news, (not that it's much), is that MB recognized the poor original design of the gasket and improved it so when it's replaced, (be sure to get the improved gasket), it should be done with.
I also have a '92 300 4Matic, (third owner), but mine is a TE wagon. I recently had to replace the head gasket in my car which has only 138,000 miles and you will see my posts on this subject when you do a search. Personally I love this car, though there are many who avoid this era 4Matic like the plague because of some of the problems that they are known to suffer from. But given the space, comfort, ride, traction, and good looks of the car, I think it's a worthwhile tade-off, (knock-on-wood). Good Luck.
1962 MB 220SEb "Fintail" Sedan
1963 Vespa VNB4T Motor Scooter
1992 MB 300TE 4Matic Wagon
1995 Subaru AWD Wagon