2000 e39 M5, Jet Black with black full leather interior and Burl Walnut wood trim, all options except rear shades, which were not available with full leather option on the e39 M5, Bluetooth added last year...I have owned it since new and has been serviced by United BMW, 108,000 miles and just broken in good... The dealer offered me $24k on trade. I have it listed in AutoTrader for $30k...what should I expect to sell it for?