There is no cabin air filter in a Z3.
The chain will last the life of the engine and there is no recommended change interval.
6.9 liters
most likely 91
If you have a newer BMW with the 20 pin Data connector use a wire to connect pins 7 and 19, turn the car ignition to position 2 count to 11 and both the oil and check engine will reset.
6.9 quarts
louisville slugger
You need to purchase a reset tool. You can order one from Bavarian Autosport.
There's a good step by step procedure with photos posted here: http://www.bimmerdiy.com/diy/e36oilchange/
The BMW z4 replaced the BMW z3 in late 2002. The BMW z3 was introduced in 1996 shortly after staring in a James Bond movie. Not as easy on the eyes as the z3 but just as nice.
http://e30world.com/Maintenance/BMW-E30-Sparkplug-Change
the 328i BMW if it is the M52 engine should be using 5w30 synthetic oil, same as the 2.8 Z3