Poly would help it hold up to the humidity better. It also doesn't have to go from top to bottom. So, you could install it so it doesn't touch the substrate. Also, as you said, it's cheap. So, replacing it isn't costly. A bigger problem, for you, is that it needs about a half inch gap behind it to allow the hooks to go through, but I sure you can figure out a way to make it work.
But, it's a project for down the road. For now, you should just focus on the essentials: maintaining heat and humidity, security, and getting him to eat regularly. Upgrades can wait.