[dangerous]

I suspect that the seller was not experienced with the 944 and misdiagnosed the problem as a bad head gasket. With many other cars, it would be a logical conclusion and it may be true. When a car overheats, the head can warp and the HG can blow. However, with the 944, we know that oil cooler seals are a problem and this is most likely what occurred.

At this point, the only thing we know (based on PO input) is that you have overheating and milkshake in the oil. This usually points to the oil cooler seals. I would suggest that you attack this first, then see if you have solved the problem before going deeper. replacing the OC seals is a PIA the first time you do it, but it's relatively cheap (if DIY) and can be done in one day. Flush you cooling system, get your radiator flow tested, and ensure your cooling system is up to par. Make sure your oil is not contaminated with water. Run it and see if the problem repeats.