We inherited the exact same lamp in our foyer. At first I wanted to replace it, but it's kinda grown on me over the years :o) We had the same question as you the first time the bulb needed to be replaced. As I recall, what finally worked was holding the lamp firmly between two flat palms. One flat against the bottom of the lamp, and the other flat against the top plate, fingers split around the cord. Then... press together for traction and turn your hands in opposite directions. Good luck! Susan

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You can buy wafer lights that attach to the regular junction box you have there. no need to make holes. .https://www.homedepot.com/pep/WAC-Lighting-Disc-6-in-1-Light-White-LED-Flush-Mount-4-Pack-FM-306-930JB-WT-4/313488381?g_store=&source=shoppingads&locale=en-US&&mtc=Shopping-B-F_D27-G-D27-027_016_INT_LIGHTING-NA-NA-Feed-SMART-NA-NA-INTERIOR_LIGHTING&cm_mmc=Shopping-B-F_D27-G-D27-027_016_INT_LIGHTING-NA-NA-Feed-SMART-NA-NA-INTERIOR_LIGHTING-71700000082087352-58700006970236884-92700066746315637&gclid=Cj0KCQiAi9mPBhCJARIsAHchl1xIytL8alkptBIx8H4TvK12LxneoarqCRl1FccfRoSD3_pG6OvMou0aArQnEALw_wcB&gclsrc=aw.ds The second hanging light in the hallway, I would convert that to "recessed" or wafer light as well. I dont see a need to have a hanging light there. In the stairwell its self I would swag it out away from the wall, and use LED bulbs in it.

do you mean a pane of glass? if so I dont think you will find it, especially since its curved. take the one from the very back and put it in its place.