I highly recommend not going that route with a laptop. Look at it this way: if you find a compatible chip (i.e. same socket) and it happens to be slightly better performance wise, it may not match up to the motherboard in regard to TDP or power required to run it. Some chips are 35 watts, while some are 44 watts, for example, even though they may be the same socket. Furthermore, a chip with better performance tends to put out more heat, which may overwhelm the stock heat sink and such, which in turn can turn into a messy situation and ruin the whole laptop.
Finally, it is a major PITA to take apart a laptop.