I am teaching myself boat maintenance mostly on my own using web forums, books, and the occasional mechanic, rigger, or specialist when the shit gets real. I’ve collected a few numbers of people I can call. One of my favorites is a general boat mechanic who is pretty good at everything, not great at anything, but knows exactly who to call when the situation is over his head. I bet you will find one of these types of guys in your area by asking fellow boaters who they call when in need.
The best quick-reference book for everything from canvas work to weird engine sounds is Don Casey’s Sailboat Maintenance. It is what I always start with before diving into a project or even a simple fix. After reading the section pertaining to my desired work, I then know enough to knowledgeably Google for details on my particular equipment.