2.5 ltr lux engine question, oil in the coolant?

[ian d]

help, i have just noticed today that i have got a dose of oil in my coolant tank. it must have happened in the last few days as i check the fluids every couple of days.
i'm not very familiar yet with this engine, request a bit of info, has anyone had similar and is it a difficult fix?

i see from another topic that the oil cooler is integral with the oil filter and a failed seal is likely in this series of engines, is that correct? head so far seems ok.