Be careful about hacking the software on your camera, I'm sure it will void any warranty that you will have with it.

I guess I can't recommend one specific book to explain what I was talking about. I'd go to Borders (or equivalent) and look at some of the "complete digital photography" books. You're looking for info on exposure (specifically how it relates to digital cameras) and post-processing (Adobe Photoshop).

Scott Kelby's books on Photoshop are great when used like recipe books, for example to know how to properly sharpen an image or correct perspective.

The histogram is a graphic representation on the exposure of your digital file. You have to shoot first, then it either shows up or you have to press a couple of buttons depending on the camera. When you learn what it is and how it works, it's possibly the most powerful tool you've got in a digital camera (top five, any way). Make sure whatever book you end up with clearly explains this, and you feel comfortable with the way it's presented.

Shooting RAW is a file format, like jpeg. It's much different than jpeg in that it takes a conversion program to turn it into a "useable" file. Some versions of Adobe Photoshop have a converter, it may come with the camera and there are other third-party options as well. It's a little more time consuming but can help you get the highest quality file that you can, versus jpeg which is quicker to work with. Tradeoffs, know when to use which type. Scott Kelby's books explain a little about RAW, but the book that explains the histogram should also talk about RAW files.