On Eclipse Kepler (4.3) and Papyrus (4.3), I was unable to find a way to update the view (class diagram) from the model (model explorer.) If I created the operation by dragging an operation node from the palette to the class in the view, the operation was added to both the diagram and model explorer.
You need to switch to the Papyrus perspective in order for palette view to show up.
I just blogged about this and a few other annoyances. (I realize this question is old enough that you've likely given up, but I found it while searching for a solution to this same problem.)