Since you are just starting out, why not go with Photoshop Elements instead? It is a "light" version of Photoshop and will do most of the things you'll need. Also look into Aperture and Lightroom and see if one of them will meet your needs, too.
I use Aperture for 99.9%of my post-processing, only going into CS3 when I want to do something more advanced than Aperture is able to do, such as layers or special filter effects, etc.