My driver side window has been experiencing some difficulty and hopefully someone here can tell me what I need to do to fix it.

It goes all the way down and will start to come back up but when it approaches the very top it just starts jumping and wont actually close the entire way. You can hear it going da da da da da when it hits the top as well.

I've asked around and heard its more then likely the gear inside the door panel has broken a tooth or what not. What part do I need to order to fix this, how hard is it to get to the motor/gear and are there any special tools I need?

TIA
Larry D