No software is necesary to do that. With the grafitti area showing, you tap and hold your stylus on the button you want to change. A list of installed programs will pop up and you can select which one you want.
I found the answer i needed! It doesn't change ALL the buttons, but it does change the least-useful one into the most useful one! It changes the Find button into a Home button, and when you tap and hold, it brings up a menu of most commonly used apps.
It's a little nameless "Free Utility" at the bottom of this page.