Hi,
I take we are talking about a 112 V6 Petrol engine?
If so then the oil to water cooler mentioned is the engine oil cooler next to the oil filter housing, their are a couple of rubber seals between the cooler part and the oil filter housing the seals are inexpensive probably take around an hour or so to do, also check for oil leaks at the bottom of the oil filter housing these seals go very hard and brittle and flatten out over time very common issue apparently.