to do the work on the steering wheel disable the airbag system for at least half hour because the srs module can hold voltage in its capicators and go off.
procedures to disable airbag are on the w201 service disc, if not i can send you documentson how to do it.

if the car has been sitting for 5 or 6 years i would check and replace whats necessary. Also gas goes bad after sitting for a few months. I would clean out the entire fuel system throughly.

For the brake issue, the calipers may have gotten stuck after sitting all those years. do a through inspection of your brake system and make sure the hoses arent cracked, the bads are good, the calipers arent stuck. Also you want to bleed the brakes because you should replace the fluid every 2 years. brake fluid brakes down as it gets older. Make sure you depressurize the abs system before doing this.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)