>>can i get a live feed of video from my HDV cam in to the canvas in FCP<<
Yes. In FCP's Log & Capture settings, set Device Control to "Non-Controllable Device" and use Capture Now. But I'd recommend also rolling tape in the camera just in case a problem occurs with the live capture ... it can happen.
That said, I do not know of a way to do the chroma keying live with FCP.
-DH