Hehehe the answer is YES!! Overclocking will certainly void your warranty.
If you plan on overclocking it, do it smart, use baby steps, 3mhz (max) at a time, and repeat, If you get to greedy and fry the cpu, definetly voids your warranty, but i quess that a risk all overclockers are willing to take, like I said overclock smart. It only voids it if you get caught. say u damaged it, resore the cpu to normal clock settings and return it
My neighbor did that and all was good.
keep us posted
-Good Luck-