Dash smoke 1977 300D

Have experienced following:
1. Attempt to start - no crank and smoke comes from driver's side speaker area. Wait 10 minutes, try again, cranks and starts fine with no dash smoke.
2. Attempt to start later - again no crank, more smoke. Wait 10 minutes, cranks slowly but starts, no smoke.

Examination under dash reveals oil around ignition switch. My current thinking is to rebuild the vacuum pump and clean out all the vacuum lines I can reach.

What to do about the ignition switch? As I understand it, the switch is attached to a vacuum element that must have been polluted. It seems like the switch itself is now polluted too. Should I replace switch alone after vacuum pump rebuild? Or switch and vacuum element together?

Are these parts available through Mercedessource.com? I see the vacuum pump rebuild kit, but I am not finding ignition switch references.

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