Indeed I would reconsider the difficulty rating...
Been there, did the fix myself with a kit. It is a lot of work, much more than I had anticipated.
If your on Renntech I sort-of took over another thread about a top, there are a couple pics there as well as some discussion of the process:
http://www.renntech.org/forums/index.php?showtopic=17836&st=20&p=94287&#entry94287
If you are
not a hardcore DIYer and do not have someone to help you with the stitching I would recommend you find a shop willing to stitch in a new window with the canvas still on the frame. The entire convertible top (canvas & frame) is surprisingly easy to remove. Most shops want to remove the canvas from the frame, that is where it gets expensive.
Also see this thread where we touched on the subject:
http://986forum.com/forums/showthread.php?t=15564&highlight=window
See also:
DYI rear plastic window.
Cracked Plastic
Replacing plastic back window '01 Boxster's Top