You have to destroy the case to pull it apart, so It's not worth it now I reckon.
Generally the pcb and all the components are coated with some sort of sealant coating so its probably ok.
But.... if down the track it plays silly-buggers I would get a new case and open it and give it a good clean and check the soldered connections to make sure there is no obvious degradation.
These units are expensive and problematic to get a full replacement so its worth the effort to maintain them ourselves.
Silicone spray is the only thing I would recommend to use without carving the case open so as a halfway measure you could drill a hole in the case (provided you had an old case and could see where you can safely drill an access hole for the spray nozzle) and spray some silicone spray in there.

