Newbie questions aren't stupid, but lots of the old-timers around here would prefer if you at least try searching the archives or googling before asking questions.
You'll get many different opinions on the oil change question. I tend to change oil and filter ever 3,000 miles regardless of the lights but I'm running Castrol GTX. The Synthetic guys probably run 5,000 miles or more between changes. (BTW the lights are really 2 sets of lights: 1) oil service and 2) insection) There is a tool available to reset, but it's much cheaper to simply jump the correct connectors in the diagnostics port with a short piece of wire. I don't remember the procedure off the top of my head, but if you search the archives, you should find it.
1990 535i 5-sp., except for 16" M-Contours, cd deck, and clear corners, completely stock. 226k and running strong