Just a quick note - not all e9X 328i come with the GM transmission.
Mine is a 2007 e92 328i n52. I bought the GM transmission filter plus gasket from rmeuropean and got around to changing the fluid today. Lo and behold, I get under the car and see the yellow sticker instead of the green sticker. Odd...how can this be...
Then I looked on the transmission itself and saw a very distinctive ZF stamped logo. Confirmed my car came with the ZF transmission via vin decoder
lesson learned - double check with the vin decoder before buying parts
http://www.bmw-z1.com/VIN/VINdecode-e.cgi
GA6L45R - GM
GA6HP19Z - ZF