I replaced the following oil seals in my E90 320i recently,
1) Engine Oil Filter Housing
2) The 2 vanos sensor oil seals
3) Engine Oil Sump Gasket
4) Engine Oil Pump Oil seal (I was told normally the whole pump is replaced but my workshop customised an oil seal for my oil pump, save alot of money)
5) Rocker Cover Oil Seal
6) Vanos Motor Oil Seal
You guys might wanna check out the engine oil pump whether its leaking, cos mine was leaking really badly. Need to hoist up the car, remove the bottom undertray, from the oil sump area, shine up towards the firewall where there is a silver heat shield, from there if the engine oil pump is leaking, you can see splashes of oil on the silver heat shield and leaking all the way down to the gearbox housing.