Disconnect the battery negative first, then the red plug connecting the airbag to the wiring harness, probably down under the driver side dash near the cruise control box. Remove the torx screws, then unplug the airbag unit. Mercedes recommends storing in a secure place, face up (plug side down)....all this from the service manual for my 560SL. I don't know anything about modifying the horn/molded black plastic facia to go back on the car without the airbag though...or maybe you are just going to disable the airbag by unplugging it?

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1986 560SL
2002 Toyota Camry
1993 Lexus