Yes, chimps tools do work like a charm, the only thing sketchy about them is you need to hotswap the new hdd (it goes in place of the dvd).. Hotswapping is relatively safe, but I don't look at an 8-10GB hdd the same way as an 80-400GB.. If you kill your stock hdd then you just need to buy a chip to replace it with a new one.. Kill the new hdd, and you gotta deal with warrantees.. I've hotswappeed many many times without incident, but every once in a blue moon somebody posts a horror story..
Also, don't bother with chimps UDE installer unless you only want to run linux, he's a linux guy not a gamer and his package doesn't install anything fun..