The oil change opinions will fall into the usual 2 camps: "BMW engineers know what they are doing, stick with the factory interval" or "change it early/more frequently than the factory interval for peace of mind, if nothing else". I don't know that there is much empirical data to support either position when it comes to our cars.
The oil itself needs to meet BMW spec LL-04. It is critical to use an oil that meets this spec, as the spec relates to the oil being a low-SAPS oil, which is what our diesels require. In the U.S., Mobil and Castrol make oils for LL-04. You can also find some Euro oils that are imported by web shops that meet the spec.
The battery is located in the trunk on the passenger side, behind the wheel well.