a simple Google search for 2008 BMW M3 clutch kits brings up 3 different website that seems to sell a clutch kit for our cars called "Spec" Stage 5. for around $1700.xx blah blah.. I wouldn't buy that and Hope UUC comes out with a clutch kit before my ///M needs it..
I would do my own clutch when that time comes..... But I must ask, what early indicators are you feeling or getting that says a replacement may be needed ?
I track my car at the minimum once a month and I have yet to feel any difference in my clutch compared to day 1. And I easily Easily out drive my stock brakes each time.. (my brake search has begun) sorry
With that said, I drive my car Properly Hard and she pushes back and wants and takes more... and my Clutch is still Solid.
Hope you car is ok.. GL