Ok. I've never hired a designer before so I don't know much about how this sort of thing might be done on iPad (or in general for that matter) myself.
I'm still not clear on what your work flow would be. Would you be making a sort of "prototype" in tools that you know that I have to then translate to the actual GUI or would you be working inside the Mac Xcode environment making the GUI files themselves that I can then plug into my program and use?