Hello I'll try to answer you questions.
Photoshop CS2 is free to download, so very worthy investment.
Also Paint.net and Gimp work fine, but might have trouble with PSD files (but I have SNES template in PDN format that Paint.net uses).
Feel free to ask questions as they rise, and we have some guides and tutorials available on the forum somewhere (usually in the FAQs, Guides, and Templates section).
And learning the cover making at basic level is surprisingly easy.
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Making Vertcal SNES covers for games that have Horizontal cover made already is usually quite easy.
At easiest simply copy/paste the front image (DO NOT DISTORT THE IMAGE, BUT IF NESESSARY DO SOME REBUILDING) into the template.
Eventually you should learn how to clean the images yourself so you can use scans instead of ready covers as source.
Then find high quality screenshots (Capture from emulator or Youtube, or simply do Google search for suitable image) and then input those to the template.
Then copy the backtext from Gamefaqs, if that is not available find the image of back cover on Google or Ebay and write it (sometimes/often you can find the whole back text by typing the first 2 sentences of it in to Google) and input that to the template.
Then find out what the barcode and SNS code and write those into the correct spots of template.
Then check the lagal text part and correct the publisher and maker of the game and correct the year.
THEN DO QUALITY CHECK SO SEE IF YOU MADE MISTAKES OR TYPOS AND FIX THOSE.
Then flatten (term meaning combining the template layers intop one layer which even the simplest printing programs understand) and save the image as JPEG, and give it to the community to critize for quality check.
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Same goes for the N64 but those need making the yellow background of the back cover and green background of the spine, but those are still bit beyond my skills (or Paint.net can't do them, at least I have not managed to use the color adjusment correctly).