Oil laden PCV valve in 2002 Chevy Malibu?

[Changed]

A relatives car has a thick oily substance on the PCV valve and in the valve cover where the PCV valve is located. Given this indicates that it has not been changed in a long time and that the oil was probably not changed often, how can I be sure that there is not any substantial damage to the engine? and what parts of the system should be cleaned given this oily valve?
The relative just bought the car.

 

[JLittle]

The only way to be sure of the internals of your engine is to remove the engine and tear it down for inspection, but oil pressure is also a good indication of engine condition. Poor oil pressure indicates oil passeges blocked or more likely worn out pump and bearings. You can buy additives that you add to the oil to help beak down the sludge befor you do an oil change.