when ordering the replacement glass make sure you specify the correct thickness.
I just replaced a french door window,
I pulled out the rubber gasket on the inside, then the plastic inserts on the out side pressed in to make them loose. Dont pull the rubber of therse as they are co extruded and can be put back in again.
then the glass came out from the outside, make sure to keep and plastic packers that may fall out.
The do the same again in reverse. The gasket may be brittle, you can pic it up fairly cheap, or put it in warm water to make it more maluable.
Rob