|"is it ok to overclock like you said with the stock fan given by intel?"|
Yes, you'll have no problem with the stock heatsink. At 9 x 333MHz, you'd only be increasing the overall CPU clock speed by 300MHz. That's really not much & is nothing to worry about as far as cooling is concerned. The biggest performance benefit is from increasing the FSB from 800MHz to 1333MHz & since your board officially supports 1333MHz FSB, you'll have nothing to worry about as far as that's concerned either.