I purchased the CD that the guys at RepairFlix.com sell and it was well worth the $11 bucks I paid on E-Bay. Basically, to repair you just resolder the cold solder joints on the circuit board. They suggest doing ALL of them which takes a couple of hours, but if you're feeling lucky, just do the ones of the several largest components on the the circuit board. These tend to go first since they will be effected most by the deisel vibration. To get the board out of the silver box, just bend the metal tabs. There is no neat way to do this unfortunately.

I was also very lucky at my local bone yard and got a working amp for my 82 300D for $10 bucks, but this was unusual.

Good luck and let us know how you made out.

PS... this technique also is what they recommend for repairing the climate control unit and the tachometer sending unit (see my post on tachometer fix for a tool-free first try though)

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Mr Goodfahrt (pronounced FAIRT... means "good trip" in German)

1982 300D Turbo Pastel Gray (off-white) 200k+(?)
newbie but willing