I actually bought my manual M3 without knowing how to drive stick. I've heard that it's easier to learn on other cars, but I've been driving my M3 for 3 years now and 40k miles later with no clutch or transmission problems. It's just practice and it helps to understand how the clutch/transmission works. If you can find someone else's stick to practice on, hey that's great, but if not, I don't think you should worry about it. Get good with the M3 and driving other sticks will be way easier! :)