Is there a way to animate the replacement of one object by another in Keynote? In Keynote, I would like to show some text and then have it replaced by an image. It would be awesome if I could do that by using the cube effect, having the text and image on different faces of the cube and then rotating the cube so the photo replaces the text, but I cannot find a way to do this. I cannot even find a way to get multiple build effects to run simultaneously. 

Is it possible to combine a build in and a build out animation in one step? If so, how do I do it?

If that is not possible, what are my options for creating a presentation where a text item is replaced with an image while the rest of the slide stays the same? Magic Move does not seem to handle replacing things, only moving them around.
It is possible to have objects run their animations at the same time. This is done in the Build Order window, which is available from the Animation palette (button at the bottom labeled "Build Order") or via the View &gt; Show Build Order menu item. Set one of the 2 animations to fire normally, either "On Click" or "After Transition". 

Set the second animation to go immediately after the first one, either by setting its build order number to 1 more than the other, or by dragging and dropping in the Build Order window so that it is immediately below the other. Select the second animation, and now you have the option in the Start menu to start "With Build x" where "x" is the build number of the animation directly above it. 

So, by setting one item to have a build in of Cube and another item to have a build out of Cube and setting them to go at the same time, I can get the effect I want of having the one replaced by the other.