UKPassats

hi all i ve got a rattling noise coming from what i think is my oil pump chain . the old girl a 2004 passat 1.9tdi awx has done 213k and has served me well over the years shes had regular servicing all the time ive had her .so my question is how much of a job is it to replace the chain and oil pump?,do i need to remove the engine to do it or can it be done in the car ive taken a look underneath and things look rather tight there?. any help on this would be much appreciated thanks