If you do a search on this site you will find posts on this subject. As I understand you open the porthole & pry out the gasket and screen as one with a screwdrver or similar tool from the inside. Check the posts they are pretty good. Here is the link to the manufacturer for replacements or you can do it on the cheap with some home depot screen. www.pompanette.com/home
Good luck! Todd
Yes, A piece of cake. Just pull the Gasket / Screen from the inside, clean whats left. They still sell the OEM replacement screen w/ gaskets they have the glue, just pull and stick. The windows maybe hard to close at first but will become easy after a while.