Hi Tracy reading your thread seems a lot of good advise ,the caliper problem should be a easy fix and if you have already tipped a load of money in it ,its like walking up a hill once you get to the top you have done it, so it may only take a few more steps to get to the top but for you to decide weather it worth it !
no new z 3s any more so i would think not that easy to get another one .
Wish you well and hope you can solve the issue .The cars have many common parts with other bmw s and seem very reasonable on price compared with other cars out their.
All the best ,Mick.