Buy an Intel Mac: the SDK only runs on this platform
Learn Objective-C: the UI must be written in Cocoa
Read the iPhone HIG: user will not accept a Windows Mobile look and feel or Windows Mobile interface conventions
Port your data model and controller layer. You should be able to use C++ for this. Note that MFC is not available at all. If you have not used a MFC pattern you need to redesign
Implement your new iPhone UI in Cocoa Touch. This will be written in Objective-C