I'd say take it to a MB only shop, have them do a PPI, and pay them for it. There may be other items in line for repairs before you worry about door locks, heat and cruise control

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95 E300D gave away
77 300D, 227k, station car
83 300CD 370k, body gone away to the rust gods, engine is in a Yota pickup, going strong
89 190E 2.6- 335k, no more
79 VW FI Bus- 154k summer driver
59 VW Beetle ragtop- 175k
12 VW Jetta- 250k
74 MG Midget-78k