For Photoshop 7.0 I recommend going to
http://www.phong.com and just doing all the tutorials there. After that just play
around for a bit with what you have learnt, then go to
http://www.good-tutorials.com to learn different textures. Just search for the ones you want to learn (I recommend water and metal ones, as they serve the most purpose and look the best.
Photoshop is quite easy to learn (on an intermediate level), it's
just a case of having time, effort, and google
good luck