||06-06-2009 05:36 PM
There should be glazing beads either on the inside or out that can be popped out using either a screwdriver or scraper. Becareful to not damage them so that you can reuse them. If you do not already have the replacement sash, you'll need to make exact measurements of the width x height. Taking the IGU out is a little bit harder. It is done best with a deglazing tool which most DIYers don't usually have, but it can be done with a 5-way(scraper).
Have you thought about just having it done professionally? The cost should not be too bad, plus they can do it quicker and easier with the right tools and knowledge.