In terms of valuing the car, the best thing to do is have a look at the classifieds adverts in print and online. Find a model similar to yours and price it accordingly - values for R129 SL vary greatly at the moment. You can find them for between £6000 and £14,000. How you sell the car depends on how much time you've got. To maximise the Mercedes' value, you'll need to sell it privately - but that can be time-consuming as you'll need to take pictures, write a decent description, and answer lots of questions and phone calls. At the other end of the spectrum, you could sell it through an auction house but you'll have commission and fees taking a bite out of your selling price.