Pics please!!! Mine has the same oil bath as Peter's which is actually not what I thought it would be at all. There's no impeller at all. As far as I can understand its centrifugal force of the cup spinning at the bottom of the quill that "slings" the oil out and up to the top of the upper bearing. I know they can fail.... but having looked it over my thought is the failures are likely either from running dry, or too much gunk built up over time. Hence I would never convert to a sealed bearing.
Anyway if it had been an oil bath I would have recommend a full quill tear down to remove all the gunk that accumulates over decades. I don't know anything about how your machine works though so????
JeffD