The front one is the engine and the rear one is the transmission. Being that you're unfamiliar with cars, it'd be better for you to have someone who knows how to change oil help you. You may avoid a catastrophic mistake if you have some guidance the first couple of times. If you make a typical beginner error like not getting the oil filter on right, you could ruin the engine.
RepairPal Certified shops can diagnose and repair your 1997 BMW 328i. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.