I am in the process of replacing another front panel on a tank, and I can tell you that if it is the bottom panel, you will have to basically rebuild the tank from the ground up. Everything else sits on that panel, so you will have to remove and reinstall all the other panels once the replacement is in. The hard part is the disassembly and trying not to do any further damage. Not impossible, but very difficult. Typically the plastic frames get pretty beat up if not broken when trying to get them off. I get my glass panels from Portland Glass and use GE RTV 108 or 103 silicone. Call a few glass shops with the exact dimensions of the panel for some quotes. Should be a couple hundred bucks or less. Good luck.