+1 for twelve. It'll make more sense if your were jumping to an i7 rather that 2nd gen i5 to 3rd gen i5. which two cpu models are you jumping from and to? is there a substantial difference in clock and turbo speeds?
also it might not be that easy to do this because you need to perform a BIOS update before swapping out you cpu with new one. you must first check if such a BIOS update is available or not.
if you can share your desktop's model no/name, we may be able to help you check if a BIOS update is needed and available.