If you have your heart set on marriage, by all means, go for it.
In my opinion, asking a girl to marry you is supposed to be one of the most romantic moments in a woman's life. She will always look back on it and the way you proposed may come up numerous times in your future so what ever you do, do it right!
I wouldn't know how I'd propose because I haven't found a girl I am willing to marry yet and if ever I'd pop the question, I'd want it to be personal.. (like at the place where you met, something she's always fantasized about etc) It will be one of the few moments I'd be caught being romantic