I agree with Panther F. However if you want something quick and you can't find a local supplier of a small pinion puller, you can fashion your own device.

Take a door hinge plate and file a slot in the middle screw hole. Once this is done you slide the pinion gear up through the hole and then slide the motor shaft into the slot you filed. Place the hinge plate across a vise, and then with a center punch pound the shaft out of the pinion.

This is the same Idea as Green Amphibian suggested but the modification to the hinge plate gives you a one piece metal plate, and it is a little easier to manage.