I did have it appraised by an auto body shop back in '84 when I first purchased for insurance purposes.
Part of my dilemma about selling the car is due to the fact that I haven't driven it in almost 18 months. It was running fine at that time but many events and much travel transpired and before i knew it 18 months had passed.
Do I spend a little money to get it running and cleaned up a bit then try to sell, or
Do I spend somewhat more money to do some minor body work, new paint job then try to sell for big $$$, or
Do I try to find someone who would rather take the car somewhat "as is"
Here's my 2 cents:
1. Appraisel from 1984 is not relevant. Value is determined by comparable cars offered for sale and having sold.
2a. If it ran 18 months ago, have the gas drained (before turning the key and having the fuel pump send grubby gas through the system), Fill the tank, charge/replace the battery, check the oil, and turn the key and let the fuel pump pump for 20 seconds and then try to start the car. It will probably just start. I think it is MUCH more marketable if you can drive it than if it is not running and if it was running 18 months ago then it is likely that the work to get it running again can be as minimal as changing the gas and charging the battery.
2b. If it does start, change the oil, coolant, brake fluid and you are good to go. Check the tires for cracking...
3. Take a zillion pictures of it and set them up on a photo hosting site like photobucket or ... Take pictures of the underside. Take pictures under the trunk mat, under the carpets if you can, engine bay, under the parcel shelves behind the seat - anywhere you can to show the presence or absence of rust. Show everything good and everything bad you can about the car with photos.
4. Post here and on other MB forums - decent chance that you will find your buyer that way. (Yes, become a full member so you can list your car here)
5. eBay is great exposure if you have a well-documented running car.