Originally it swung out, hinged on the top, but this was long ago caulked and sealed shut. Getting it out proved to be not a big deal, and just by luck I had a piece of scrap plywood that fit the opening without cutting... with that kind of fortune I'm just bound to break a pane of glass! Once inside I could do a good inspection. No real structural issues, just a few coats of glazing (a few too many!) and paint that was already half off. Inside was originally stained, later painted white, then stripped poorly, and then some finish put on. No care was used in not getting any stain, stripper, etc. on the panes so these will need some work to clean up. The inside of the panes are textured making this even more of a pain.
I tried using a toy I bought a few years back to remove glazing. It attaches to a drill, and has a handle with a built in guide. You're supposed to walk it along after setting the depth on the tool and it should just cut out the glazing without damaging the window. Well maybe it was all the glazing but it just road on top and had no real control. So I gave up on that and just used patience, a 5-1 painters tool, and a light touch with a hammer. In the end I managed to get all the glass out intact. Next step, stripping everything down....
Closeup of paint and glazing condition