Sivers has some good advice on this, though it may not answer your last questions:
TLDR:
1. Reduce your big idea to “Version 1.0”.
2. Write a simple overview of what it does.
3. Write a detailed walk-through of every click.
4. Break it up into milestones.
5. Make your first milestone a stand-alone project.
6. Post it at elance, guru, odesk, vworker.
7. Hire one from each.
8. Continue with the one you like best.