Good call! I would also check to make sure there aren't any other pins that are also hooked directly to 5V. Also if you hack the card, I would recommend doing it in a way such that the bypass capacitor near the 5V pin is now connected to 3.3V as well, that way you still get the benefits of that capacitor. If that's not possible I'd add another bypass capacitor for the new 3.3V supply near the chip's VCC pin.