Questions about Intel processors and Graphics card?

I have a laptop, it's a Toshiba L655-S5058, when I bought it, it came with an Intel Pentium processor, and sometimes it runs a bit slow while playing games, I'm not looking for top tier graphics or anything (Starcraft II), but just less lag and smoother gameplay. Can I replace my processor with a better one such as an i3/i5/i7/Quad Core? And my graphics card is an Intel(R) HD Graphics, can I replace that too? Thank you.