Hi there, I'm a new member too and I have been through something similar. I'm 24 and although I've never smoked (except for trying cigarettes like once or twice just because), I suddenly found out last November that I had a very leaky valve and a severely dilated aortic valve and root. I was born with a bicuspid aortic valve, but since I was so young when they found it I was just told my heart had a "sticky valve" and I was fine. Since it never bothered me no one ever explained it to me (until my doctors very suddenly discovered I needed surgery, that is).
Like yours, my parents were told it wouldn't bother me until my mid-forties or so, if ever. And for a lot of people with BAVD, that's true. Lucky you and me, eh? We turned out to be special. Obviously I can't tell you what will happen or what you should do, but I can tell you how it's all gone for me so far, speaking from the post-surgery side of things.
As far as choosing a valve, most of all I wanted to avoid needing heart surgery for the rest of my life if possible, so in the end I chose to go mechanical. I got the On-X valve, which so far has performed exactly as it should. Plus, the INR range (and thus, the dosage level) is lower than for other valves -- my surgeon told me, very specifically, that my range is 2.0-2.5. I've also been told by countless nurses that the ticking noise my valve makes is much quieter than the other mechanical valves they've heard, like the St. Jude's valve.
I'll be honest -- I don't regret my decision so far, because even though my surgery went well enough I'd rather not repeat the experience if I can help it -- but the INR thing has been a bit irritating. I know some people get the hang of it after a while and sail along with stable INRs for long periods of time without issue. I have not been quite so lucky; mine likes to lull me into a false sense of security for a few weeks, only to drop back to 1.7-1.9 and aggravate me all over again when I'm least expecting it. I'm still learning as far as diet and all that goes, though, so it's still likely I'll stabilize in the near future. I'm told it can take a long time for your body (and your lifestyle) to be properly adjusted to life on coumadin.
Whatever valve you choose, do your best to chill out as much as you can while you wait for surgery. I know it's so much easier said than done, but try to relax as much as you can! I recommend LIGHT walking and LIGHT yoga -- both are great for your heart and for stress relief without being too strenuous -- and don't push yourself. It's okay to be scared and to freak out a little -- goodness knows I did -- but know that your heart CAN be fixed and you CAN recover from this and live a full and healthy life. I and many others on this forum are walking, talking proof of it.
Given the similarity of our situations, I'd like to add that you can feel free to PM me if you want to talk in more detail about BAVD, valve choices, surgery, etc. I'm no health professional by any means but I'd be happy to answer any questions you might have to the best of my abilities.