I bought the 1999 528i. The previous owner maintained and serviced everything well. With records. However. He has been putting low grade gasoline in it for 11 years, but says it's been fine. I would like to start using premium. Will switching right now have any adverse effects? And is it...

It's been about 7.000 miles since the car has been serviced This is the first time I'm servicing it while it's under my ownership, What exactly do they do? I think they change the oil filters, and put a new oil if I'm not wrong. Do they change the oil pump as well? Just need some basic info on...