I was actually puzzling over this several months ago myself. I blogged about it and got some good discussion with other writers regarding the various methods for both writing and revising.
You'd likely find the three posts/discussions on the bottom of the page the most helpful since they deal entirely with different ways to get started and keep going once you put pen to paper.
Robin, I would simply write the story while it's fresh in your head and worry about editing, fleshing, creating a more three-dimensional world once THE END is placed. While writing, read books, read how-to writing books. I find them to be inspirational and motivating while I'm writing.
Jump in. You can always revise, and as Pauline says your brain probably knows more about good story structure than you think.
Then, after you've written for a bit, start reading writing books and join a good writer group. Really, no matter what you write there is no better group than RWA (romance writers of america) for learning the business and craft. SinC (sisters in crime) also used to have a group called guppies that offered some really good information.
Lori http://www.loridevoti.com
I'm another "jump in and write" girl...provided you do know the bare bones of the story you are trying to tell and have "sketched" the main characters.
I've paralyzed myself with writer's conferences (which are great, by the way...but led to my overthinking my story) and books on writing and the like. I'm an overanalyzer by nature, and it works to an extent -- because I've thought through my plot, etc...but it's also freaked me out so my inner editor takes over before I can even let my id out.
So it sounds like you've got the skeleton of your story and know where you're going. At this point, begin to write and the mechanics can come with revisions.
I agree with most posts....just sit and get your story out before you over think it too much. If you feel confidant enough to even say you "have" a story, you better get writing! Don't let the story slip away before you have it out on paper.