85 500 SEL greymkt Tune Up / stalling / no heat

My parents own an '85 500SEL grey market (not a standard US model). The engine idles poorly, stalls frequently, and recently heater has stopped delivering heat shortly after engine reaches operating temperature. After reading other posts, I'm suspecting a vacuum leak may be at the root of all/some of these problems. Service records from previous owner indicate that stalling/rough idle was a problem for them as well.

I'm a diesel fanatic ('66 200d, '79 300d)-- I hate all the electronic stuff on this car, but would like to do what I can to improve this car with the basic equipment I have: my brain, common sense, Fluke digital multimeter, timing light, (no vacuum equipment).

I'll start with new spark plugs and wires--what parts are recommended? Don't want to buy MB dealer parts unless absolutely necessary.

What do I check after replacing plugs and wires?

I'm trying to keep parts cash outlay for this project to $100.00 or less. (diesel tightwad)

Thanks.

[mhingram]

Your heat may well just be the monovalve. If you hit the buttons does it came on again then disapper if it does replace the monovlave. This is a $30 fix. You can also just pull it and check if there is a hole in the rubber that is your problem. On rough idle. You can throw huge amounts of money at it and still not fix it. I would recommend taking it to a good local shop and have them scope it and stick it on the gas analyzer. They can at least tell you where to start.
m