I think that model is on a ring internally so there isnt a way to do like the bigger ones, you would have to take the screws out and take in half and you will the the brushes and can replace.
Some power tools have a thermal reset switch built in. It sounds as if the thermal overload is faulty, or the unit has overheated. Check to insure the cooling ports of the motor are not clogged with sawdust.
