First, check the tranny. If there is a long hesitation going into reverse, this is an early sign of wear. Hard shifting can be adjusted out but slipping means trouble. Check the push pushbutton unit on the dash. Even if the AC doesn't blow cold, it should at least switch from hot to cool and defrost. A new pushbutton unit is $400 and a rebuilt is close to $200.

It's a good idea to inspect the vacuum pump although I don't know how. A total vacuum pump failure can break the timing chain.

Timing chain. either check or have checked the timing chain stretch.

With that mileage, the motor should be OK but it really depends on the price you plan to pay.

$1200, expect a fixer-upper

$1500, maybe runs OK but looks crappy

$2000, looks ok, runs ok...far from perfect.

$2500, Getting better.

$3000 and up...the interior better be clean and it better run decent.

Over $4000 It better be awesome.

My 2 cents anyway.

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1982 300D Turbo "Helga"
380,000 miles