If you go to the 107 forum on Benzworld or the Vintage forum here on Peachparts, you will find a lot of information on "Trigger Points". That is what they are commonly called. Mercedes have various other names for them like "release contacts" (in engine manual). These points cannot be adjusted. They can be cleaned if they get oil on them, but no abrasive should ever be used. They run at low voltage/current and don't burn out. What does wear, is the fiber cam follower. Unfortunately replacements are very expensive. But this is probably not your problem.

I would first adjust timing. It should be set so it advances to about 27/28 BTDC at 3000rpm. At idle it will be at TDC or maybe 5degBTDC. If you can't get any advance, then there may be something jamming the internals of the distributor (maybe caused by installation of the "electronic" ignition. What was installed? Was it a Pertronix? Sometimes centrigugal advance is jammed anyway. That requires disassembly of distributor to free up the centrifugal weights.

This link shows some pics of the trigger points and the centrifugal advance weights.

D-Jet Distributor Removal & InjectionTrigger Points Repair - Mercedes-Benz Forum

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5