Yes, if the car is a color that is unique in the image...selecting it can be easy...(or just changing that particular color as Matt said).
The best tools in photoshop is the ability to use layers. Think of it like old school cartoons where they would layer transparencies over one another to create the final image. You can do the same think with photoshop but with many, many different options. Basically, you want to create a layer that is just the car's paint...then you can change that layer to whatever color you want, without changing the rest of the image.
I always start by making a duplicate layer of the background...this way you can always go back to the original image. To select the car's paint, you can use any of the different methods of selection...the magic wand, the magnetic lasso etc. What I like to do, is to use one of those to make the initial selection, then create a layer mask (from the layers pallet). Then zoom in and paint the layer mask on or off, at a high magnification, to make the mask just right. You can do something similar by using 'quick mask mode'. Once you have the selection or the layer with a mask...you can play with all sorts of adjustments to change the color of the car.
Sorry, that isn't much of a step-by-step...but I can't teach you the basics, not right now anyway. Search for photoshop tutorials and concentrate on selections or extractions. It takes practice to get good, so don't expect professional results right away.