For anyone interested in doing any sort of photo edit for this type thing (ie. the navi hack), I would HIGHLY recommend paint.net. It is completely free (legitimately free) and it is very similar to Photoshop. The interface is very easy to use and it does not take much to learn the basics of it. I use this program all the time at work (for our software). Only catch is, you must be running Windows (but who am I kidding, I am probably the only person here running a Mac)
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To get it, go to:
www.getpaint.net.