So I can just overclock the IGP without overclocking the CPU right?
I should say this though. When I say you're shortening the lifespan of the CPU by adding voltage, unless you give it way more voltage than your cooler can even handle, it'll still last for years. You're shortening it from nearly infinite to something like 5-10 years. Not a big deal, when you consider that you'll want to upgrade before then anyway.
If you're still hung up on it, Intel offers the Performance Tuning Protection Plan
for only $20 dollars for the 3570K. It's a one time, no questions asked replacement, no matter what you do to the CPU. I have it myself for my 2500K. I don't think that I'll ever need it, but whatever, $20 for a new CPU, if I ever do
need it is a small price to pay.