Its fairly easy, from memory all you need is a screwdriver and a socket set. Its basically three bolts/screws, 2 at the front of the window and 1 at the rear.
The way I done it was the open the rear window and undo the back mount, then undo the front two and take the window out. The attach the rear fixing to the new window and line it up and screw it on, then screw in the front two, job done. Wont take you long.
1 thing though, dont do what I did and try it on your own, make sure you have somethere to hold the glass when your taking it out and putting it back in, aswell as to hold the back of the mounts for the screws as mine kept falling out.