If it's a wooden canopy you'll be able to drill or bore holes in for light fixtures yourself, I've done that before using a bradawl.
If the plastic frame to the tank is a support of some sort, then a crack is a problem. If this piece of plastic (I really am trying my best to picture it but have no idea) is easily removed and actually has nothing to do with the tank itself or supporting it, then you could just remove it.
Tell you what, here's what I'd do:
1. Buy the lot.
2. Take the tank apart from the stand: def. keep the stand and canopy.
3. Put the tank outside.
4. Fill it with water.
5. Leave it and see what happens overnight.
If it leaks, then you've a problem so get rid of it.
Tanks which are not structurally sound rarely explode like the great stories we all know about describe. They generally leak first, and THEN explode. So, fill it and check for leaks (or, if it explodes straight off then you won't have to :P hehe)