distributor questions - '92 300ce

[sonsmechanic]

Some history: My son purchased a '92 300CE this fall, 113K miles. Ran fine when we bought it but soon developed a slight miss on acceleration. Took it to an independent shop... had the throttle body cleaned and the rotor replaced... along with other needed service. Did great for a short while but soon the hesitation was back along with other symptoms - occasional ABS light, cruise control malfunction, reverse lights sometimes inop., A/C not cooling. I searched the forum archives, replaced the oxygen sensor, and was about to order an OVR, but then... the car's symptoms progressed to rough idle, then to occasionally dying, finally to... dead. After towing his car home I started checking and found the distributor assembly completely disintegrated. It appears that one of the bolts that hold the rotor onto (what I think is) the rotor adapter, came off, and chewed up the inside of the cap along with the rotor and adapter. I am confused because there is no bolt that holds the adapter onto the camshaft... I was able to just pull the adapter off. I am trying to buy the necessary parts from MercedesShop.com but need to know all the parts required. My questions are...
1) Is the part that the rotor screws onto the "rotor adapter"
2) What holds the adapter onto the camshaft?
3) What is the plastic part of the distributor that is behind
the adapter that the gasket and cap fit onto?

And in general...
1) Is this car one of the ones plagued by wiring harness issues?
2) Should I go ahead and replace the OVR on principle?
3) Are there other problems consistent with the symptoms
that I should check?

I appreciate the wealth of knowledge available on the forum and your willingness to help.