I upgraded my friends laptops CPU which featured a A8-4500M to an A10-4600M (I updated the BIOS first but I dont recommend updating the BIOS first, as Ive read people having more trouble after updating the BIOS before installing new CPU, what I recommend is to try new CPU first if laptop boots up and works as intended then you are good to go but if it doesnt then install old CPU back in then update BIOS then replace with new CPU and see if it works), it works with no problems but as jimpz has said sometimes the upgrade doesnt work even when the sockets match, so it can be tricky in that, the only way to really find out is to replace the current CPU with the new one.
If you want upgrade then you have two choices that will give you the biggest performance jump (most of it will be on the GPU side not on the CPU side): A10-4600M or A10-5750M
Also dont forget to get thermal paste too