I am with "fhotoace" on one very important point. It is much better (and easier) to take a good photo in the first place, than it is to "fix" it, later, in Photoshop.
The start of a "professional" looking photo is in knowing how to use the camera in the first place. Photoshop is not going to fix a badly focused shot. It is not going to fix a badly posed or composed photo. It is never going to make an image as good as one that was captured properly IN THE CAMERA.
What do you think "professionals" did BEFORE digital cameras and Photoshop?
But, moving on, Photoshop is an ideal tool for what used to be called "post shooting," or "darkroom" work. Before Photoshop, there was a LOT that could be done, after the shot was taken, to make changes and even "tweak" shots that weren't quite perfect. But it took a LOT of time and effort. Yes, even some sweat and tears to make happen what SHOULD have been done at the time the shutter was released.
The good news is that, with digital cameras, and applications like Photoshop, the time to make these "post shoot" changes was vastly shortened. The five, ten, fifteen minutes spend in a darkroom, adjusting an exposure could now be done in one or two minutes. But still, that one or two minutes could be elimitated by the five seconds it takes to make sure one's exposure and angle were correct while still behind the camera.
So, fine, Photoshop exists and people will STILL depend on it. It is a wonderful tool and I admit to using it. And I use it a LOT. Besides being a replacement for a film darktoom, it is also a great creative tool in it's own right. It is a POWERFUL tool in the hands of a knowledgable user. A Photoshop "Power User" can create things that were, nearly, impossible, in the times of film photography. It is an indespensible tool and is the center of my work as a freelance designer. By far, in my opinion, the BEST tutorial for Photoshop is the "Classroom in a Book" series, by Adobe. It is the one used by Adobe Certified Trainers.
A website can show you a series of tricks and effects, but a good tutorial or class can show you how to use the entire tool. With this knowledge, you can learn how to do ALL the Photoshop is capable and how to create your OWN effects and tricks, not just copy someone else's technique.
For $700, you might as well learn EVERYTHING Photoshop has to offer you. Why buy an entire 767 jetliner if all you are going to do is taxi your friends up and down the runway? Why buy a two hundred thousand dollar sports car if all you are going to use it for is to fetch groceries?