Thank you for the responses, even the ones who's who think I'm in over my head.
I do know what the project entails and I'm very comfortable with doing the work. It's what I've been doing within companies for 12 years; including budgeting for projects and setting time lines, allocating resources, etc. What I don't have is experience with budgeting, and contract creation, for working as a contractor.
If it was as simple as doing the math on what my time costs while working for projects within my company the budgeting thing would be easy, and maybe that's as simple as it needs to be. However, I don't want to be way off (high or low) on what the going rate for this type of work is in my area (Chicago).
I suspect the consulting rate would be higher since people working on their own, outside of a company, have other costs that people working in an organization don't.