HP 620

Hello, i want upgrade my friend´s notebook, but im not sure. NTB already has 2Gb RAM(1slot is loaded/1slot is free) .. i want try uprade to 8Gb - 2x4Gb DDR3 Can i do it? Is that compatible? Next step: Uprade CPU- I have question...Is possible chnge CPU or is it fixed to MB? If its possible...