Alon the top sides of shower stall ordinary sheet was installed back in 1993 when our has was built. That Sheetrock is covered by wallpaper. Over the course of time moisture from the shower spray has caused the bottom edges of the Sheetrock is swell and bulge (looks like lip). There is now a very small gap between the shower stall and the sheet rock. I need to know how to best seal this gap and how to deal with the deteriorating sheet rock edges. Thank you.