Depends on how much the car is being sold for. It can be repaired. Box needs to be opened up and seal changed, or you can just bolt up the leak from the small hole. Its been done before and works a charm. I personally wouldnt let it put me off, because after all im a mechanic but it isnt ideal lets be honest, but as far as the functional aspect of the box it wont effect anything depending on how bad the leak is. Are they sure its coming from the breathing holes at the bottom of the box or is the leak coming from the breathers at the top of the box, sometimes when the gearboxes have been serviced and the clutch fluid overfilled, it pisses out of the breathers causing a real mess and can lead to something that looks like a leak when actually it isnt.
