Yes, it is too big, The pololu driver can only deliver 2A ( as it says in the page ), and to get full potential out of the stepper you would need a driver with more power.
It would work however ( ie. the pololu driver won't fry :) ), but you're wasting money in some sense.
You can easily find steppers rated 2A, that will fit perfectly with the pololu driver ( some hints above, also alltronics++ ).
About overheating, that's not a problem, you just need to cool it down ( ventilator works fine here ) if you want the put it at max current ( it will shut down if too hot, so no risk frying it here either ).