I love my BMW Motorcycle. Actually I've got o0ne and wifey has one too, but hers does not get a lot of riding time. Next to my e34, its the most fun to drive. Mid-life crisis sure worked out well for me.
Rebuilding a manual tranny, actually sounds like fun. I've done an auto Volvo tranny once and always wondered how hard it is do to a manual. My daughters manual tranny in her 1992 535im occasionally grinds when going into 2nd no matter how nice you shift. It's very occasional, but I'd imagine, that over time, the more it grinds, the more likely it'll need to be repaired. I don't know a lot about manual trannies, but I'd suspect a bad syncro or something, correct? it's weird, cause most of the time the shifts are butter smooth. Really it's about once every 2 weeks you get a grind, and thats not with hard shifting, just real easy shifting, so it's quite a suprise when it happens.
Any way you can: Ride hard, pedal hard, drive hard.