Check in on the AMD overclocking thread and ask there.
My suggestion for a possible overclock is to ONLY OC the Northbridge.
I have not OC'd an apu yet, so that is why I suggest asking for advice in that thread.
However one can usually get very significant performance increases especially on AMD chips with faster NB, and can often be bumped with very little voltage increase. Which would mean very little heat increase over stock.
The results will not be earth shattering no matter what, you simply have no way to dump the heat from a big OC.
But 10-20% increase in cpu thruput should be possible. This is very dependant on motherboard and bios, how lucky you got with the chip, etc.
Do NOT OC your computer until you feel very confident...