Peter,
Since I lived the dream, I almost never tell someone not to go for what they want in life. Someone long ago told me that the first test of whether you have what it takes to become a gca is to be able to avoid or resist all the people who tell you it is a bad idea. (Which will be just about everybody if you hang with people like I knew (fam, friends, college professors, etc.) It also helps if you are young enough to not know all the things that can go wrong. (I walked into my boss's office on my 29th birthday, quit, and decided to start my firm in TX where I knew absolutely no one, nor had any prospects.....my mantra was "what could possibly go wrong." It probably was just dumb luck, together with my stubborn streak, that allowed me to feed my family for 37 years. So, either complete ignorance or a plausible back up plan need to be in place, LOL>
And, Ian is right that it helps to be in a very practical situation (i.e., be very rich, or at least have a working wife who understands and is bringing in money, no or grown kids, but it sounds like you have some of that going for you.) Ditto, Ben, as I always put new hires on a 3-6 month "probation period" to evaluate their suitability for the biz. Honestly, I could tell if a new hire really had design sense within weeks, not months. Short version, while desire is key, you must have some innate talent for it to stick (at lesat past the first recession you happen to hit.)
From my somewhat dinosaur-ish perspective, I say sure, read all the available gca books, but the real training you will need is in the practical, not theoretical, perspective. Any designer who hires you won't feel they need much design advice for the first few years or so. So, you would need a benevolent boss who understood where you were headed (and those do exist) and be willing to put up with you as you learn. Like most other things, it's a people biz, and if you hang around the kind of people who can help you, you have a chance.
Good luck, and if you prefer a longer conversation on my perspective, message me here and maybe we can talk further.