no quick answer, take it slow and chip away at the putty when you have removed the putty you should find a few little nails holding the glass in place , pull these out and if you are lucky it will come out, putty is linseed oil based and sometimes puty can be softened by rubbing oil into the surface, a few little pin holes in the putty will let the oil get further in,..p.s. be prepaired for some breakages, even the pro,s expect this to happen.
willie
April 2006