congrats on your first car! have you been looking around in ford focus forums, such as focusbc.net? you can ask them about good ford mechanics. or even make new friends and invite them over to help you out!
by stuttering, do you mean it bounces around at low rpm's once you start it?
and before you replace the battery, check the voltage with a ohm meter! if it reads around 12.6 volts, then you're good
as for window, taking your door panel off would probably be the best way to pinpoint the actual problem with your window. it's almost fall/winter anyways! just keep it up for now =P
sorry i'm not much of help xD hope you do find more help though! good luck