Put original ROM, etc... on phone

[Synth3t1c]

So I cooked a ROM, and it works great, but I'm having a problem with a couple of keys on my keyboard (the function key needs to be pressed uberhard and the period isnt doing so hot, the spacebar sometimes inserts 2-3 spaces, and some keys insert twice). I need to take it to the sprint store so they can (hopefully) fix it, and I don't want them to blame it on the cooked ROM, ior changed radio or whatever.

How do i get the sprint defaults back?