Now a days its not difficult to learn about photoshop. I think web is the best and cheap way. If you 'll spend your time for learning then you can become expert within no time. I want to share with you that my fiends they are web developer and they have learn everything on web with out any instructor. I mean web is a ocean of knowledge.
If you wish to become expert really, you have to start learning and practicing now and maybe after few years you will be somewhere near "expert" The possibillities of PS are so huge that you need to spare a lot of time and effort to be real expert.
The first thing I would recommend to do is experiment on your own. Go to File>New, this will open up a new canvas to work on. Try using the options at the top to get a feel for the program. Next start using the tool bar which is located on the left side of the photoshop. Once you have a good feel for photoshop, search for tutorials on here or through google. Look for tutorials such as "Basics of photoshop", "Basic designs", "basic banners"... These tutorials will help you get a good feeling for the program. Remember that practice makes perfect! Don't expect to be an expert upon downloading the program. There's much to be learned!