Personally, I would be inclined to keep the Intrepid and buy without a trade-in. Only because I enjoy doing the mechanic "work" when the car has troubles. And it can be nice to have two cars. Of course a lot depends on your situation, do you have room for two cars, do you like to work on your car.
KBB puts a trade in for your car @ about $2600 and private party around $4300.
I wouldn't ever want to trade a car in unless I absolutely needed the money to put towards the new vehicle. You could always buy the new car, pay for it completely with the loan, then privately sell the car and put all of the money into the new car loan.
The toyota yaris gets pretty good mileage for your commuter needs, and it has a low price.