Thanks for the replies. I have no doubt I can get it out--just did not want to break/ruin anything. Six point socket and big cheater bar, no problem.

Incidentally, this vehicle has been serviced according to the MB schedule by the dealer up to 160,000 miles. This drain plug appeared as though it had never been touched. Also, the transmission drain had never been removed either--black paint still around sides of plug head where it meets with the pan. Makes me wonder.....