Sell it yourself on the classifieds here, or even craigslist. The dealer will not give you what you could get for it on your own. Remember that they will have to turn it and make a profit it on it as well.
Just like anything else, dealer is the last place you want to sell stuffs (cars, boats, guns, etc ...) to.
Do they buy them up front? Some don't and some do.
How much do they give you? About 25-30% less than what you can sell to another individual (ie, 2cooler).