Tanks are actually fairly easy to fix if you have the time to put into it. Especially since it's for herps and you don't necessarily have to hold water. You have to clean out all the old broken glass, scrape off all the old siliconed surfaces. You will probably have to remove the trim as well and clean all the old silicone out of those pieces. Clean with rubbing alcohol, and get a piece of glass cut to the dimensions of the hole. Lay down a bead of silicone, insert the glass. Tape it in place and let cure for 24 hours. Once dry lay down a bead of silicone on the inside corners and bottom and smooth out. Let cure for another 24 hours. Silicone inside all the trim, and reattach to the top and bottom. Let cure again. I have helped my boss (pet store) build many tanks over the past 15 years, and have had to replace glass in them occassionally from normal use around the warehouse. Accidents do happen!
D80