I recently sold a 28BHS. Had to do repair to wall under window in front bedroom due to leak around window, ruined the paneling inside. I removed the window, but you can just loosen screws inside around window frame, and installed caulking tape under the outer frame. retighten the screws and it will squeeze out excess caulk,( may need to use rubber mallet to softly tap the frame in to seat the frame against the siding) then I used thin piece of wood,(actually a sharpened popcicle stick) to cut the excess around the frame and removed unused caulk. Makes a nice looking job without having to apply regular caulk that will need to be removed later when recaulking is required. Tape caulk stays soft, so easier to repair/replace.
Retired Firefighter from Texas
2013 Jayco Flight 32TSBH