This short should be called "Writing Your First Script Phasa 1 not Makeing Your First Movie" Way to vauge and stilted. Every film idea is based on a film idea that has already been produced. What makes your idea original is how you as the writer / film maker envision and present it. So basing your property on something that isn't in 'public domain' isn't a writers concern. Also, as a writer you don't worry about the cost of production. That is the concern of the Producer or Studio. There is lots of freeware avail. for script writing ie www.Celtx.com and for help you should contact W.G.C.
How To Make Your First Movie - Phase 1: Writing