Its not in the owners manual because BMW wants to make money by having you come in and getting it reset. The reset isn't only for the oil thou. It can be for maint. also. So you may not want to reset it just for oil. You can get your own reset tool on ebay or something.
2001 BMW Z3
3.0i straight 6 engine
M badge series
Dinan cold air intake, Dinan software, Dinan High Flow Throttle Body, Dinan stage 2 suspension upgrade, Dinan Strut Tower Brace, 18 inch wheels, and don't forget the fancy pedals.