Hi,
The steering wheel will fit as it is just a 16mm bolt that holds the wheel in, however, there are two types of slip rings and two types of airbags.
Stage 1 Airbags and Slip rings were fitted to any Z3 released before March 99 and Stage 2 Airbags were fitted to Z3s that were released after March 99.
You'll need a Stage 1 Airbag with an earlier Slip Ring if you have a 97 Z3. Stage 2 Airbags have different connectors that only work with the later slip rings, and these slip rings will not connect into your car.
If you're looking to fit the following wheel then
@Craig Giblett has a stage 1 Airbag for sale I believe.
If you're trying to fit the smaller SRS wheel - this one - then I have an airbag and slip ring for sale, PM for details.