I am sorry to hear about your medical problem.

You should not have any trouble selling it. Does it have auto or manual transmission ?
Do you have the service or parts records for all that time ?
Fair selling price is very subjective. I suggest you set a price which you would be happy to get for it and advertise it at that.... if it does not sell within a reasonable time period you can lower the price and try again.

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html