Even with stock cooling, 3ghz is usually easy enough to achieve with a stock clockspeed of 2.66.
Increasing the cpu speed on it's own won't cause the CPU to fry... it will only increase temperature moderately. Increasing the CPU voltage is what is likely to burn it out.
OC Rule #1: If you don't know what you're doing, don't touch voltages. You're more likely to break it than fix it.
There's plenty of heatsink benchmarks around, if you decide you want to push your overclock further... the new thermalright ultima-90 looks pretty good. But ultimately it will only give you a fraction more performance than you get with stock cooling.
Also, you will void your warranty by overclocking, so only do it if you actually need the speed (or the glory) and you can afford to replace the chip if it fails.