I want an i5 cz my i3 is too too slow and keeps hanging. So is it possible to get it changed into i5 or do I need to get a new one ? Also I wanted to know if Windows 8 would work on a Windows 7 based laptop. As far as I have been told it would not last long enough. Just wanted to confirm.

First, I don't know of any laptop where the CPU is replaceable. However, Windows 8 will run fine on an i3