Volvo: 1992 Volvo 4-dr GL breather box, dr gl, leak oil

Question
What is a breather box? - is it essential to the running of the car? Is it usually repaired, or replaced?  @ cost?

Answer
R,
It is where the crankcase fumes are transferred to the intake so they are run through the engine to be eliminated. If the breathe is blocked too much pressure will remain in the crankcase and cause engine seals to fail. It could also have bad seals and leak oil along the side of the engine. Cost to repair/replace $300.00 give or take depending on the labor rate.