Ok ill look on 7zap at pictures/ parts and have a look in the manual. As I've said I'm trying to amass info so I know where to start.
I think you have your answer from Evripidis, doable but fiddly and awkward. Scant mention in the workshop guide except remove and put back with a couple of torque figures and no doubt renew seals. I can help a little with the location, looking up at the back of the engine look for the holed bracket that supports the upper inlet manifold and it is just to the right.
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I am sure how the oil separator (called pressure control valve in workshop guide) is for servicing, I.e open it up and clean, suspect largely a sealed unit, but I do remember a member repaired the membrane and it cured their problems so this must be accessible. Dread to think of the cost of a new oil separator and be careful not to break the clips on the hoses or that will be more expense.
Please do post how you get on and the part number if you would as I am