I responded to Carl G on a message he forwarded to me from you RE the windows
. In case it doesn't make it your way, I have the same trailer and have had all my windows refurbished.
When I took them out, there is just an inner trim-ring that's screwed to the outer frame. Just remove this ring - likely the existing caulk and butyl will hold it in place, but you may want someone on the outside, just in case. Really it should just be butyl and the trim-ring that keep the window sealed and tight.
This is true for all the windows.
RE the brackets for the molded fiberglass window guard, when I redid the inside, I tabbed some wood to the fiberglass on the back side of these mounts so that they'd have something to bite into. I actually tabbed all the wood supports b/c Bigfoot
only glued these strips to the shell interior - good from afar, but far from good. Over the years, the glue just let go on mine. The upper cabinets were barely holding on when I stripped her down.
FYI - the company that made your windows is up here in Summerland BC. I had them refurbished and they're like new - black powder-coated, new screens, seals etc.