Please don't take this the wrong way, but are you sure you mean ball joints?? Because what you are describing sounds more like the swivel housings on the end of each side of the front axle?
They are a shiny sphere, about 8-10inches in diameter? If it's these, you will need to replace a number of oil oil-seals to get them oil-tight again.Incidently, LR refill them with grease not all.
If it's the actuall ball joints, they are filled with grease not oil. Easy and cheap to replace.