Photoshop is a truly amazing program. But yea Lynda.com is an awesome source for tutorials. If you want free brushes and not sure where to get them go to Free Photoshop Brushes at Brusheezy! you can find alot of great brushes to make some sick stuff with.
So far I've had 3 full-time courses dedicated to Photoshop in school. I use Photoshop to texture all 3D models I make. There's a good reason for it's price and it's popularity.