i don't know if the brushless motor has bearings or bushings, but lube them. see if that squeak doesn't go away.
unless something is wrong (gear mesh to tight, over geared, etc) a brushless motor shouldn't go bad in a month.
and yes, you can upgrade to a higher mah battery no problem. and, im not 100% (haven't really checked out the brushless versions yet) but i think you can even run a lipo battery.