I don't have remote locks, so I can't help you there.
There should be 2 belts, one to drive the water pump, power steering and alternator. And another for the AC. An OEM pair is about $21 at
www.eap4parts.com There is a lot of "controversy" over changing the automatic tranny fluid. If you go to
www.bimmerforums.com and do a search there are tons of posts about the subject. My automatic has 120,000 miles on it and it runs absolutely beautifully, so I'm not gonna touch it.
My manual says the oxygen sensor "must" be replaced at 100,000 miles (i'd guess just for emission purposes), and at about 105,000 miles it failed (well, gave me a CEL).
www.eap4parts.com has it for $93.95. My dealer wanted $168.
Anyways, I couldn't tell much difference with the new one vs. the old one. Although my fuel mileage went up just sightly.