i am considering buying a 2009 macbook that has 10.8 on it. the seller can't find the original software discs. i would need to run 10.6 on it. the machine originally came with 10.5. is this a big deal or difficult to downgrade? is it as simple as getting a 10.6 disc, erasing the disc and installing 10.6? i have an ilife disc that i can use to install other stuff when all is said and done.