Well, I sure wouldn't sell it to a dealer! Sell it privately and use Autotrader. Go to the Kelly Blue book site:http://www.kbb.com
Get a better, independent idea of what its worth, look on Autotrader and see what other people are asking for their used Celicas. A few months back I sold my old car on Autotrader, had the ad up for a whole 4 hours or so before it was sold, and I sold it for the price I asked too.
Best of luck to you.
Your profile says you live in Alabama. Which city? I used to live in Huntsville.