I replaced my 2002 top with a 2004 OEM top with glass rear window a few years ago.
I followed the instructions from these links and it was a quick and easy project. I don't recall specifics, but these links should give you what you need to remove your top and frame.
https://sites.google.com/site/mikefocke2/installinga'03-'04glasstopandframeona'97
http://986forum.com/forums/boxster-general-discussions/20414-2003-oem-glass-convertible-top-installed-01-boxster.html