Well, that's wrong. But no, I assume you are talking about the DV6-6135dx, or some variant with the AMD A-series processor line. Unfortunately, the A-series processors aren't sold on places like newegg, and I wouldn't know where to buy them. The processor speed and the brand are ultimately what turned me off to the DV6-6135dx.
Yes you can.
Will it improve your gaming experiance? Maybe. Maybe not.
What model of dv6 do you actually own? What CPU and GPU are installed? What motherboard does your laptop have installed? (Run CPU-z and the Mainboard tab will have the specific details).