Sell it to the dealer for $500. Unless you intend to part it out. Only consider parting it out if you have a place to store the eye sore. If you want to sell it in one piece for more than $500 get the transmission repaired. Then see if you can sell it for the cost of the repair plus $600. If you can you're even considering the time and effort to get it fixed, put an ad in the paper, show it to the wheel kickers, etc...... OR sell it to the dealer and be happy with the years of service and the $500 you got for it.