Just took my window out to fix a bubble in my side. Removed all the screws from inside the frame and pushed it out. surprised that there were no other screws in the outside. There was blk sealant around the entire frame. It had never leaked. will go ck out what sealant was used and put in back in then caulk around window with approved rv caulk. Good Luck
Carefully check what your manufacturer states. Mine says that if you use silicone caulk,as they recommend,and install the window without letting it cure beforehand, you WILL get leaks, emphasis added by the window manufacturer.
Here's the skinny. I had forgotten about a technical contact I have at Fleetwood. I spoke to him this morning, and he said to do the following. Use a utility knife to break the silicon bead along the top of the window, then a putty knife or blade to break the seal against the frame and the coach. The frame is internally sealed with urethane sealant. This sealant can pull the paint off the fiberglass, so he warned me not to try and force out the windows or I could damage my paint. Clean up the coach, put on a bead of urethane, put it back together with a bead of silicon along the top and 1/2 way down the sides... done.
He also said they have worked out more favorable pricing for replacement windows, if I have a problem, call their cust service and they will help.