Need advise on body work.

yes cut out the rott and weld in some none diseased steel treat it with ecoat and do your filler work ecoat over the filler work and prime it block your primer with 120 or 180 check for any imperfections (pin holes, scratches ect) apply polyester glaze block that , ecoat again and reprime. then wetsand with 320 400 or 500 to prep for paint seal it and paint it