The bottom is definitely going to be tempered glass, especially with a tank that size. The sides might be tempered or might not. Robb is right, find the manufacturer and ask them, either on their sponsor forums on RC or directly on the manufacturer's page.
If the side isn't tempered, I'd recommend installing an internal coast to coast (C2C) overflow with a BeanAnimal design. Search for those two terms and you'll find lots of info.
Also, I'd recommend asking the manufacturer if the rear panel is tempered. If not, maybe consider putting the overflow on the rear instead of the side. If all of these panels are tempered, your only option is to use a HOB overflow. Drilling tempered glass is very risky even for experienced glass cutters. If you take the tank to a professional glass cutting shop, they will either refuse to drill tempered glass or they will offer you no warranty if the tank shatters during the drilling process.
It's a little too late now, but this is why a lot of people look for predrilled tanks (tanks drilled in the bottom panel prior to tempering the glass). Depending on your needs, maybe you could buy another tank that is predrilled and use this one as a sump?
Just my two cents, good luck.
