The high resolution version is your original image file straight out of the camera. If you only shoot jpeg, always save any work done on the file with another name so as not to change the original. The best solution would be to shoot RAW because there is so much more to work with in the file, and it never gets permanently changed.
Photoshop does seem rather daunting and expensive, but just learning a few basics first is not difficult at all. I've tried to show some friends a few tricks on Elements and was very frustrated because there are a lot of things you just can't do in Elements, or it's actually more difficult. Don't try to do everything at first, just add to your knowledge as new challenges arise. Photoshop help has gotten pretty good, it's online now and you can search for information on specific tools, etc. and the answers that come up are both from Adobe and many others, often with video tutorials. Scott Kelby's book Photoshop CS4 for Photographers
(also available for earlier versions) is one of the best and easiest to follow and includes tips and tricks that are actually useful in real life. Lynda.com has tons of Photoshop video tutorials for all levels of expertise. It is a pay site, but well worth it. Just remember to take one hurdle at a time and congratulate yourself on every one you clear. You'll get there, just have fun.