whats it like changing the tandem pump gasket bkp tdi

[jamesey]

hi ive had a smell of diesel for the last year or so but now i can see the diesel smoke burning off in the headlights at night and the smells got worse , im nearly 100% its coming from where the bosch tandem pump marrys up the the engine . ive bought the new metal gasket ready to fit but wondered if anyone has actually swapped this gasket , also the water pipe thats just above the oil cooler has had diesel on it from this fault and its gone all mushy if that makes sence , any more info would be great , im hoping i dont need to take the plastic housing off underneath it .