The problem is, I don't know a thing about OC'ing.. :P
I want to OC though, it's just that im afraid i might end up breaking my processor XD
Also, I think that a regular i5-2400 would suffice my needs (mostly gaming) right?
The 2500k would be the best option. For overclocking all you need to do is make sure you have a good cooler such as the cooler master hyper 212 and boot into bios and change the multiplier. The multiplier multiplies by incriments of 100mhz, so 40x multiplier would mean 4ghz!