$300 is probably a bit high for a tank that is damaged...
Where is the crack?
Have you tried reaching out to reptile owners? THe overflow boxes can probably be removed with a few razor blades and some elbow grease, and the holes in the bottom can easily be plugged up if someone wanted to keep a snake or something in it. You might want to talk to AWx2, he might be able to point you in the right direction for finding someone that keeps reptiles...