How do I update my graphics driver?

I have Intel GMA x300 and I want to know if it's possible that I could update to Intel HD 3000. I'm using a MacBook, when I purchased it it was leopard, but I've upgraded it to snow leopard. If I could update to any of these, also I would like to know: ATI Radeon 2400 or higher or NVIDIA 8600M or higher. I'm doing this so I can play L4D2 and Gary's Mod.