There is most likely a hole in the metal skin to pop off the window. Don't use metal tools when unclipping the window, as it might shatter. Tape window with burglar-tape (duct-tape I think it is) to the top frame. Unbolt the bolts for the metal skin and undo any wires and plastic plugs (might have to push them in, as the that might be attached. I think the window mechanism is boltet to this metal skin.
Haven't done mine yet, so this is qualified guessing.
M.