When you buy a Oil Filter from the dealers or GSF or an independant, they should sell you a pack with the Filter, the large O-Ring for the canister, a tiny O-Ring for the end of the bolt that secures the canister and a new washer for the sump plug. I also find the main dealer also often supplies a new part 4, the washer for the canister bolt.
Parts number 3, 4, 6 and 7 here:
3 - O-Ring - 11 421 711 076
6 - O-Ring - 11 421 741 000
4 - Gasket Ring - 07 119 963 080
7 - Oil Filter Element - 11 429 063 138
http://www.realoem.com/bmw/showparts...67&hg=11&fg=30
And part number 4 here, the sump plug washer:
4 - Gasket Ring - 07 119 963 151
http://www.realoem.com/bmw/showparts...93&hg=11&fg=10
You can likely skip replacing the washer for the bolt on the canister, but should always replace the washer on the sump plug.
Tightening torques apply on all bolts please!!
Regards
Ivan