There are some differences between CS and 7. However, both of them are equally powerful and complex.
Photoshop takes a lot of learning, and you will find that there are things you didn't know even after using it for a year! Don't worry about the complexity - you need to start simple and build you way up. There are many hints, tips and tutorials on the web for Photoshop, but some of them are pretty complex. See if you can find something basic and work through it until you understand exactly what's going on!