You will need to contact Acer and find out which CPUS are competible with the board in your system. With the chipset, we could give you a list of CPU thats MAY potentially work, but that reallys wouldn't help. If they won't give you a list or can't then look at the higher version of that system that they sell and see what CPUs they have.
I have a laptop identically as yours, and upgraded to T8100 6 months ago, and runs perfect!
I have a list of processors that will fit the GM/PM965 Mobile Chipset.
Core 2 Duo
T8100 (2.10 GHz, 3M Cache)
T8300 (2.40 GHz, 3M Cache)
T9300 (2.50 GHz, 6M Cache)
T9500 (2.60 GHz, 6M Cache)
Core 2 Extreme
X7800 (2.60 GHz, 4M Cache)
X7900 (2.80 GHz, 4M Cache)
X9000 (2.80 GHz, 6M Cache)
All of these Processors have a 800FSB and will work with your system.
Cooling should not be a problem as long as you have a good brand of thermal paste.
Make sure you clean out any dust that built up in the fan/heatsink as well.
I hope this info may shed a little light into getting a decent CPU upgrade for your Acer.
Also, here are a few more CPUs that can work...
Core 2 Duo
T7100 (1.80 GHz, 2M Cache)
T7300 (2.00 Ghz, 4M Cache)
T7500 (2.20 Ghz, 4M Cache)
T7700 (2.40 Ghz, 4M Cache)