When I removed the windows
in my Trill to reseal I just had to
take out all the exterior screws. It was difficult to remove as the
ensolite on the inside interfered. I used a thin putty knife from
the inside running it along the edge of the frame to get the frame
past the ensolite. The window hole in the fiberglass shell is
"just" big enough to get the window through.
As to the riveted strip, my trailer does not have one there. It may
have been added over the years by a previous owner. If it does not
extend too high you may be able to get the window out. However,
if it gets in the way it may have to be removed.
Looking at the photo of the screws you removed they don't appear
to be too rusted so the wood that the window is screwed to may
be in good shape. Mine was quite discolored from moisture but
there was no delamination of the plywood. The screw holes were
a little sloppy so I used the old carpenter's trick of filling all the
holes by poking wooden kitchen match sticks (dipped in wood glue)
through the exterior holes in the fiberglass into the backing plywood.
After the glue set I cut off the sticks by running a razor knife between
the fiberglass and the backing plywood. This provided good holding
power for the new screws.
BTW, at the behest of a pal who is an "RV Guy" I used two layers
of butyl tape on the frame when re-installing the windows
provided plenty of squeeze out and a great seal. Also I heated the
tape up by putting it in the sun on the dashboard before using it.
I like to get the butyl tape warm enough so that it just starts sticking
to the paper tape on the roll. Also, make sure the window frame and
the fiberglass are VERY clean before installing.. I wipe it down with
denatured alcohol before installing and the put the butyl tape on the
window frame for installation.
Hope this helps?
Good luck on you project.