Trading your car in is convenient, but in exchange for that convenience you will get less money for it. Selling it to somebody will get you more money. Some folks are patient, and willing to go through the effort of selling a car to get that extra money. Others don't want to be bothered, and just take a little less for it in exchange for not having to conduct the sale. I would first suggest you make a decision in that regard.
When you look up the value of your car using the links posted above, you can choose to see the trade in value or the private party value. Private party value is what you can hope to get if you sell it to another person.
When selecting your financing options, be sure to make an informed decision. The dealership might offer you financing and, on paper, they can make it look like whatever they want. Be sure to find out what interest rate they are offering, and if they have any special incentives (i.e. 0% interest, 0.9%, or something like that.) In this economy, you should be able to find a nice interest rate if you look around a little.