There is a video on YouTube with a guy showing how to upgrade the G70 https://www.youtube.com/watch?v=i4xbILQgU8Q
However he only upgrades the RAM, HDD, and WIFI card. I am highly doubtful the notebook can supply enough power to an upgraded CPU, and even more doubtful that MSI's BIOS will support any non OEM CPU. I would contact MSI, since their support is usually very helpful even with things like this. They might even make a custom BIOS for you, but I very strongly doubt that this is possible.