Thanks for the feedback. Just wanted to post an update to the problem. Towed the car to Silver Star Motors in Vienna, VA, and Peter was able to diagnose the problem.
First, the head gasket was fine, apparently changed by the previous owner (I've had the car for about 18 months). Guess, when it overheated, the thermostat was stuck causing continous overheating - should have been changed when the water pump was replaced by the last shop. Then the misfire was coming from a blown valve cover gasket which caused oil to seep into the spark plug holes. Once the thermostat, plugs, and valve cover gasket was changed, the thing runs like a dream again.
1993 300CE Garnet Red
18x8.5 ADR M-Sport wheels (Hyper Silver)
Metal Master brake pads
Semi-gloss black front grill insert