How much of a window should be replaced?
I think you would be best off calling the window manufacturer's service department.  Double paned windows are usually made as a unit: two pieces of glass with a spacer between to separate them and seal the opening.  The space is often a vacuum, or filled with an inert gas like Argon.  It might be possible to replace the broken pane, but you would be losing all the other benefits of a double-paned window: insulation, soundproofing and blocking heat and UV from sunlight.