electric lawnmower repair?

I have an old black and decker electric lawnmower that has served faithfully. It has now stopped working. I think the brushes probably need replacement. I took four screws out of the motor housing but still cannot get the two pieces of the housing apart.
1. are there internal parts still holding it together?
2. Assuming I do get the two halves apart, how are the brushes replaced?
3. What else to look for?