I would go get Lightroom 3 personally, i think after the initial hour or two it takes to get your head round all the sliders and folder layout you will be lost without it.

Photoshop is brilliant if you know where every filter and effect is hidden but Lightroom allows you to change most aspects of an image quickly and none destructively, it allows you to arrange all your images into categories within itself and enables you to arrange files so you can choose whether to keep or delete them.

If you can help it, always shoot in RAW, more data is saved and allows for more tweaking and editing with less boundaries than JPG, Imagine RAW as being a nearly infinitely editable file that you can always return to "how it was shot in camera" if you want, but a JPG file is like getting an image that you cant really do a lot with and once the changes are made you cant go back to how you took it in the camera.