Yes you can, but you will need to take some time to open the laptop. The two CPUs are for the same socket so it shouldn't be too much of a problem. I upgraded my i5 to a 3630qm with no issues. Just make sure you connect everything properly and you should be fine.
i7 3630QM | 750GB Hard Drive | 1080p Full HD Display | Corsair Vengeance 16GB | GTX 660m | Windows 7 Ultimate