@simonm, I was leaning toward the use of a small wood planer or using a very delicate hand with a very sharp chisel. Having read the suggestions above, I think it may be best to go to the pros. If the shop where I was learning, which regularly repairs instruments, cannot repair this one, it is certainly beyond my skill.
This guitar is made of beautiful wood and when I speak into the sound hole, I can hear the resonance. It is an old 70s model, classical guitar, luthier built, Even with the cracked bridge, I still feel that to have purchased such a lovely solid-wood classic guitar was a good choice. I wanted a luthier built guitar and I got one. It just needs some love.
Thank you all for the wonderful suggestion, especially as regards the unknown glue. It would be a terrible shame to destroy this guitar by using the wrong method.
I don't want to play like other guitarists; I want to give voice to the song of my own soul.