Can't be done.
The ability to upgrade most laptops is pretty much non-existent. For one thing, the power and cooling are optimized for a low-wattage APU. Secondly, even if you could find an APU of the same socket type it wouldn't work unless they added support in the BIOS (and why would they do that?).
A good APU costs closer to $200 and still might not be as good as you'd hoped.
Finally, the APU shares some of the System RAM as video RAM so a better APU in your laptop would likely be massively bottlenecked by the slower System RAM (many laptops have a single stick of 1600MHz memory, and since a good APU starts being bottlenecked below 2133MHz Dual-Channel it works out to roughly getting HALF the video performance you paid for..).