If your battery went dead, it's probably your voltage regulator. I was driving down the freeway when mine went bad -- started missing badly, stopped and started a few times, then it was done.
It's attached to the underside of your alternator and two phillips screws hold it in. Pull it out and see how long the "brushes" (two contact poles - spring loaded) are. If they are grooved and worn down, then that may very well be your problem.
'91 300E, 215K miles