I had some oil leakage on top of my camshaft cover. My car drove just around 100.000 km. My garage told me I had to replace the whole cover(witch include the membrane of the PCV), cost 280€ not included the garage labor.
So I bought myself a repair kit;
https://vanos-bmw.com/ and did it myself.
I cleaned the oil from the parts with a cleaner. That makes the brown color. I am no mechanic but it can be done. At the same time I replaced the cover seals. Total costs; 58 euro and a couple of hours and everything works just fine.