If the motor is still in good condition; bearings/bushings/windings etc, I would suggest replacing the seals. If you have an ammeter check to see if it's within the rated amps when running under load. There are some features of older motors that are better than the newer ones today, even when you step into the industrial quality. Without knowing how many hours or the conditions in which the motor operated you're guessing. A good motor repair shop could help evaluate what's needed. If the varmish on the windings is breaking down they may be able to recondition those too. Take photos into a motor shop and see if they will give you a ballpark estimate. PS. New grease seals don't tolerate over greasing and old ones are worse.