New to this also, here's what I have learned thus far. I was / am stripping mulit-layers of paint off of birch framed glass cab. doors. What a drill! hours of stripper, sand and varnish ( wax on wax off, shades of karate kid). End result ..varnished wood frame looks great. Now, going to convert some others to framed glass. After the above experience 6 hours per door, I found in easier to build my own. 4 tools required, saw, router, clamps, bisquit joiner. Built my first one, never ever having handled a router or busicuit joiner before, including first coat of varnish in 3 hours. I wouldn't even think of stripping the others, just make new ones. This all isn't the same as your cutting out the centers of exsisting doors, but maybe worth consideration.