I have a VN V8, can't imagine that it would be much different. It is screwed into the left hand side of the exhaust, just past the headers as the pipe routes down underneath the car.
My mates VP is blowing out smoke with a blue tinge when its starts or is reved in idle, so I would say the O2 sensor isn't sensing as well as it should, consumption is also a bit high. Thought would change that 1st before consulting a mechanic who will just rip him off as they have me in the past, every time i get under my VR and change what i think is wrong i am usualy right
My mates VP is blowing out smoke with a blue tinge when its starts or is reved in idle, so I would say the O2 sensor isn't sensing as well as it should, consumption is also a bit high.
Blue tinge is burnt oil, black smoke is improperly burnt fuel so his problem will be internal wear within the engine. Tell your mate to save his money for when the big dollars are required (i.e.rings or worse).