I would think, based on your description, that ~$3500 would be a fair price - but it really depends on the particular condition of the car. Make sure that the vacuum system is in good order. Lift up the floorboard carpets and make sure everything's nice and dry while looking for any water damage, esp. in the rear. Make sure the quarter windows roll up and down. If they don't, take $500 off the price. They can be fixed, but it's a pain and takes a full day to do. Check very carefully for rust on the body and on the rear wheel suspension. Since it's a repaint, I'd take a magnet and a piece of paper and check the wheel wells and the door bottoms carefully. They don't repaint cars for sport. Make sure that all major components are in good working order (A/C, ACC - check all flaps for operation-, dash gauges esp. speedo and odo, all switches, etc.). If any of these are not working, subtract more $ (esp. A/C and ACC) for each. Since it has good records, check to see if any major systems have been replaced recently (bonus, depending on what might add $$). It's really hard to put a price on it as it is worth what you or someone else is willing to pay for it. Keep in mind that you can get a minty 240D, a really nice 300D, and a good CD or TD for about the same money.

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1982 Mercedes-Benz 300CD
1982 Mercedes-Benz 240D - stick