Well, I thought I would answer this as I struggled to find an answer to a similar plight I found myself in which resulted in trial and error.
Firstly, fully wind the window down and then remove the interior 'push-button' lock at the top of the door. This can be achieved but pushing a small bladed screw-driver in the hole in the button and pulling the entire piece in an upward motion (this can be a little awkward, but is necessary). Once this is removed, pull the window winder off and you can now remove the interior grab handle. This will then allow you to unclip the door card.
Once the door card is removed, ease off the window strip seals on both the interior and exterior side of the window recess.
Now pull away the window seal from the guide rail next to the quarter-light which is to be replaced. This will reveal two screws; one at the top and one at the bottom of the guide rail. These screws should be removed and the guide rail pulled out.
With the rail out, you will be able to completely remove the broken quarter light, and slide in the new glass with little effort. *tip* use some diluted washing up liquid to give lubrication.
Repeat the above steps to put all the fittings back.
I hope this helps in your DIY window fix!
Carlos
June 2010