Just want to add my 2 cents. Got my replacement from Sunset Prosche for about $200. Just follow the excellent write-up from
http://www.bombaydigital.com/boxster/projects/window/
Not that hard a job BUT, during installation I reconnected the battery to test out the window function, big mistake! Now the airbag warning light is on continuously. Guess I'll have to get the Prosche dealer to reset that light for me.