Here's my take: if you have absolutely never seen Obj-C code in your life, it'll take a bit of a time to get used to it. Put it together with the fact that the SDK is totally different and you'll have to learn every single new method, and it'll probably take at least a couple of months for you to become an average obj-c developer if you study hard.
Instead, use MonoTouch and learn the entire SDK using C#. In a couple weeks, you'll feel right at home with all the classes, Interface Builder, etc. You'll be able to develop the app in the same way you would with Obj-C, but in C#. The demo version allows you to use everything, for free.
THEN you decide what to do. Depending on how the whole issue with Apple goes, you may decide to just continue using MonoTouch, or you may decide to learn Obj-C, and basically use all the knowledge you have already gained about the SDK, which will make the transition much easier.