That door will definitely be a hole when you grind off the rust,if your not getting a patch welded in, you will have to fiber glass it, then grind it off,then body filler,depending on the thickness of the filler you can use 40grit then 80grit,and to smooth the scratches out use 180grit,or you can use wet or dry to finish off,then prime or use spray putty,which is a primer but thicker,wet flat with 1200 wet or dry,clean up then paint & lacquer.you will get a dry edge on the lacquer if your not using a spray gun,if you are you will know you have to spray thinners on the lacquer edge to blend it in.
Chris