Found and tested the O2 sensor. Had a reading of 2.8 to 3 ohms accross the two white wires. Tested the other wire to ground and it showed OL on the old Fluke so I assume it is ok.
I will probably go ahead and replace it with a new O2 sensor this weekend. I have been unable to ascertain whether it has ever been replaced or not. Will be good exercise to replace it - will help me get over the intimidation factor.
What is ya'lls feelings with picking up a Bosch O2 sensor from NAPA (quoted price of $167.00) and installing it versus one from the dealer. I did notice that the one in there now has the three pointed start symbol on the plastic connector.
Thanks ya'll
engatwork

I have no problem buying Bosch sensors from NAPA except I think MB list is about 150+ (I'm at home). Should be many cheaper sources including many dealers that sell at list.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

IT IS FIXED!!! - I replaced the O2 sensor with a new one from the dealer and the code is no longer activated and the check engine light is no longer on. Someone from an earlier post was accurate when they said that the check engine light would come back on as long as the code was in there.
thanks everyone for the information.
engatwork