M57N2 double turbo models have ZF 6HP28 tranny but BMW didn't change the nomenclature and it's designated as 6HP26 in parts diagrams. These both fit the same oil pan. There are two compatible versions of the oil pan. Plastic one with integrated filter and a rubber gasket or metal oil pan, separate filter and a thin gasket.

Are you sure the leak is from the oil pan seal and not the electric connector sleeve? Did they change the sleeve too when oil was changed? It's advisable to renew the sleeve always because they are prone to fail.

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E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey