Yeah, the game really uses all 4 cores if you have it. It does takes a lot of CPU power, so any extra performance you can squeeze out from overclocking will help.

Overclocking by increasing the frequency is safe, worst that could happen is your CPU crash when its unstable.

But the dangerous part is increasing the voltage (which is done to allow higher clock speed), too much voltage will permanently damage your CPU, so don't do it unless you know what you're doing