After four years of working on cars bikes are pretty simple. My bike hasn't needed anything major yet but I figure I'll bring it in to the LBS if there's a specialized tool that cost more than parts and labor (So I guess professional wheel truing - I can do it just fine, but I'm always scared I'll seriously break something since I do it blind without a tension meter). Otherwise I buy accessories from them because they're an excellent shop and I've seen them talk in depth with a few walk-ins about maintaining and riding their big box bikes.