These motors have just one moving part. The armature or shaft. The bearings is usually the only thing that has wear. Replacing them is good practice for annual maintenance.
I see a lot of dead ac motors with blown capacitors or "caps" for short. If a bearing goes, you'll know it. It will be loud and usually goes out over time and the severity of the noise also grows with the wear of the bearing.
Capacitors is probably the number one reason for a dead ac motor. It's wise to keep one on hand for such an emergency.
Replacing the capacitor is really simple. Make sure the motor is unplugged. Then locate the capacitor on the motor. It's usually in a box or hump case thats on the motor itself.
Capacitors store energy, lots of it. Do NOT touch the bare terminals EVER, unless you have discharged the capacitor. To discharge, just short out the terminals to themselves, then short them out to the case ground. If your still apprehensive, work with it as if it were live by using well insulated tools to pull off the slide terminals.
If your motor is running fine, just leave it alone. Take a picture of the numbers on it, and use that to order a replacement part.
