The Kelly Blue Book is a great suggestion, the only problem is the car is old enough its not a selectable year from the pull down menu (only goes back 10yrs). If you go the NADA guide the car is worth $2945-$11250, depending greatly on the engine, if it has AC, and accurate condition of the vehicle. Without knowing which engine and if you have AC its not possible to get much more accurate than that, but if you average the average retail price of all three models you get $6,667
Wow! an SVO. They arent as sought after as they deserve to be but for a truly "great" condition car, $12,000-15,000 would be reasonable. Hemmings Muscle Machines suggests fair price for average condition would be $8,000. If your car would happen to be optioned with the Competition Prep or Wing-Delete it would be rare enough to command slightly higher prices.