Try starting it in neutral- the neutral safety switches ussually fail in park. We just went through this with a W124. No start either position. For a week, my wife would carefully put a wire in the B+ terminal and run over to the other side of the engine compartment, remove the start harness connection- and touch the hot lead to the terminal. Starts the car, then replace the connector.
She got some strange looks at the Mall with 2 kids, but was quite happy there was an easy work-around.

Michael