Problem solved. I modified my existing glass by cutting a progressive window through the artwork.
I was scared to death risking my only glass, but using a razor blade and a straight edge I managed to cut out the window and peel off the artwork. The artwork was very thick and it took a number of passes with the blade. After peeling the artwork off is where the real work began. Beneath the artwork was a thin plastic film bonded to the glass. This was really hard to get off. You have to scrape it off with a razor blade. If you try to peel it, it usually breaks. Finally with the plastic film off, I dampened the tip of a cloth with acetone and carefully wiped the exposed glass to remove the adhesive. The adhesive came off instantly.
This was a difficult job and I don't recommend it, but it is doable. I think it came out well but I was very lucky.