Christy,
I was told to put 1 to 3 drops of 30wt motor oil, not a whole squirt, at the base of the motor drive shaft. (It's the shaft that drives the bobbin winder tire.) That is where the top bearing is. As you run the motor it will get warm. The oil will seep into the bearing, combine with and soften the grease in it. The trick is you have to run the motor to get this to happen.
You can pull the motor if you want, but to put a drop or so of oil on it you don't need to. Just follow the drive gear down to the top of the motor and put it there.
You might need new brushes along with a good cleaning of the commutator on that motor. And make sure the big fiber gear is greased. Not oiled, it takes grease.
Also make sure the main shaft and everything the main shaft moves, IE the cam stack and needle bar parts are clean and free to move. If not they will bog down the machine.
Joe