Do I need to replace it or can I just clean it up & replace it when it breaks down?

The capacitor will need to be replaced. You should be able to get on at any electric motor shop, or HVAC supply house. Bring the old one with you so the voltage and farad rating can be matched.

Be sure the old one states on it " NON PCB", if it does then you can throw it out in normal trash.

If it does not state that, then it is older than 1978 and will contain PCB, ask the supplier how to dispose of properly.

Be careful removing the old one, use rubber gloves and eye protection, you may not know if it contains PCB until you get it removed to read the label.

Wear the gloves to clean up the spilled oil.