Do you have Winterboard installed? If so, the easiest thing to do is to make a theme with the original icon in it as the "modified" icon. Or else, add the original icon to any theme you currently may have installed and running. That's what I would do.
I just hate to actually mess with the true innards of the iPad, hence the suggestion to use Winterboard and theme it.
Whichever you do, if you don't do it right away ... may I suggest you e-mail that icon png to yourself now, so you'll always have it in your computer files...
Marilyn
P.S. I daresay that since you didn't specifically say you were jail broke, that Marie read your post too quick and so moved you. I've moved it back to the Hacking section...