There are lots of good books for it out there, but I think one of the best places to start is Writing Musical Theatre by Cohen and Rosenhaus. Link: http://www.amazon.com/Writing-Musical-Theater-A-Cohen/dp/1403963959
They break it down and make it really interesting- and they discuss both writing an original work and adapting a work to musical form.
I am a semi-professional musical theatre/opera actor and have been involved in both writing and theatre for a long time, I'd certainly take a look at what you come up with. I've done similar stuff with other guys from this sub (even attempted to write a musical collaboratively- didn't go great, but I'm not soured on it).
I don't really write music, though, so count me out for that. But I'd be keen on getting some work produced, so any way I can help.