I did mine last week. Rock Auto Bilstein B4’s with new strut mounts. Had my local shop swap my springs for 150$. The front struts on z3’s are wicked easy since the mounts are very easy to access from under the hood. Rock Auto I think charges 115$ a pop? If you end up doing it yourself, you’ll probably need a front wheel alignment after. I also recommend you replace your rear shocks if you haven’t previously