There's just so much more to the whole thing. Like the answers below, your best option is to have a Realtor look at it for you. I can't think of anyone who would charge you for figuring out your comps for you, and determining the value of a property or of your own property. Knowledge of the market counts a lot, plus you really need to pull up and look at the listings that were sold to see what their condition was, and what the terms of the sale were (foreclosure etc.). Conditions are changing quickly.
Anyway, you get the idea. You don't need to join realty trac to get the information you need. Just call a Realtor and they'll do it for you for free!!