Just an update that I took it to an independent BMW specialty shop (Burnaby BC) to have the seal replaced. They got the job done, but there were no "special" BMW tools used. Evident from the insert nut and flange looking mangled like a pipe wrench was used. Lesson learned, I could have done this myself and save $400. Anyways the job is done now and they do warranty against leaks for 2 years.

Thanks to all who offered feedback.