I guess I was figuring that with the vehicle being 20 years old that I could be looking at replacing a lot of rubber and electronic components going forward.
No, not really. Sure, there will be some perishing & wear on rubber components, possibly engine & trans mounts, driveshaft couplings and front lower wishbone bushes. But that's only possibly. For peace of mind get the obvious items inspected.
As for the electronics, yep there's a few common items that tend to be applicable to most face lift (late '97 on) W202. Alarm sirens & heater motor fan regulator pack up, wiper motors seize (lack of maintenance), MAF's go as you know but they are a long term service item anyway and it's not unknown for the Cam & Crankshaft sensors to pack up as well. Coils sometimes too, which again are a long term service item. Ignition switches (EIS) fail too but I don't know if that's due to the amount of use (on/off) or time period. Sometimes, I suspect it's due to the ignition being left on without the engine being started?
Personally, I'd initially inspect the drive belts, tensioners, idlers, water pump + clutch if fitted, rad condition and thermostat. If all is good keep an eye on coolant level and the temperature gauge. Also, have the PVC hoses and valve (located under the inlet manifold) inspected which is important and usually overlooked.