If the cracked pane of glass doesn’t need to be starfire, you can search around and find 1/2” glass for probably under $300. You’ll need silicone and I highly recommend the BRS aquarium silicone, it holds really really well. The trick is getting it apart. If the tank is more than 5 years old or has been left dry in the sun for any appreciable tome I would strongly consider breaking down every joint. Otherwise you could just replace the one pane which will be a lot less work but you do have to remove 100% of the existing silicone and everything and make it clean as a babies ass.
If you redo the entire tank, you’ll need a sufficient workspace and work surface that is dead flat and sturdy and jigs and clamps to hold everything true during setup. I’d mock up each pane with jigs and clamps before each stage of assembly and check and double check everything for square before the silicone sets up.