Honda Civic Hybrid  

Here is something you may have already considered, but I am mentioning it because many may not and only look at what they save in gas alon. Does what you save in gas figure out to more than you will be making for a car paymeny? In other words, lets say you now spend $200 a month on gas with your grand prix. Lets now say you trade in your grand prix for the Honda, which theoreticly gets twice the gas milage, so you will be spending only $100 a month in gas. And lets say you get a nice low car payment of $200 a month. You are then still paying $100 MORE a month than you are now. all my numbers were more or less for demonstration purposes of course, but they probably aren't too far off. And it doesn't take in to account maintenence, is your grand prix on it's way out mechanicly, etc.
Another thing you don't seem to realize, is that the cash for clunkers program is no longer running, it ended last week. So unless there is some sort of credit you can take in your state taxes, your out of luck there.
Just some things to think about.