Looking at fastlane it appears that the ignition assembly for the W107 body is somewhat similar to the W123.

I've never touched or seen a W107 so I don't know if this will be applicable. But its worth a shot. On he W123 the clearance is too tight to actually do much of anything with the assembly in place. It is easier to remove the ignition assembly to work on it than to take the dash board apart so you could get in there.

I have a mostly complete site that details removing and working on the W123 ignition assembly.

http://garnet.acns.fsu.edu/~jjs5772/W123/

This reminds me I need to finish the page.

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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.