Find out what all the options are on that car, go to MB website and build and price car to see if it really is 64,000. Then I would subtract 15 to 20 percent the average depreciation of a new car driven off the lot no matter how many miles it has because it is now a used car. I would offer them 51,500 and go up maybe 54,500 and say that you are ready to buy car right now. Don't make an offer if you are not ready to commit to it.