I have an '94 E320 and the same thing happend to me. The technician sold me a $120 little harness that goes in around the lock. He told me that there is a hex screw on the door jamb and use that to loosen the lock. The lock should slide out with a little effort and he said that the new part was pretty easy to install. Mine has only gone off that one time so I haven't yet replaced it.

I hope this helps!

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1994 E320 Cab (mine)
2001 Chevy Suburban (wife's)
1995 BMW M3 (son's)
1989 Volvo 740 GL (extra car--for sale)