I second this. I don't think Viragos are "awful," quite, though they have poor brakes and terrible starters (the early ones, at least). But parts are hard to find, and you may also be hard-pressed to find a shop to help you work on it if you get into a bind. You can find better bikes to learn on -- for example, an old Honda CB. They're everywhere, easily modified, parts are all over eBay.
As for learning how, I agree that the best way is to learn by doing. Start with simple things like maintenance procedures -- cleaning the chain, checking tire pressure, replacing brake fluid. Then move on to simple mechanical systems like rebuilding the petcocks. Move up to the carbs -- take them off, disassemble them, and reassemble them, then tune them. A good shop manual will walk you through all of these things step-by-step, and Google and YouTube are your friends. Build on what you've learned, and eventually you'll be able to do it all (with the possible exception of welding or fabrication; unless you're willing to make a sizable investment in time and equipment, you're always going to have to pay someone to do that kind of thing for you).
Learn how to be patient, because you're going to fuck up a lot. And if you're anything like me, I mean a lot.