Normally they should be able to replace that on the spot, provided that you can show proof it was not user damage. However, if the broken bit has not taken any of the pins with it and it only looks like a small scratch, you can install it and see if it works. If there was no damage to the internal circuits or the core, it should work just fine. Also , make sure the metal cap on the top is not bent or displaced, otherwise there will be cooling problems.