Hello and congratulations!

With the under tank heating pad you will need to also get a thermostat so that you can control how hot the pad gets. If it gets to hot it can burn your snake. I ordered mine off ebay and was half the price that I would have paid in the store. And you'll want it to cover about 1/3 of the bottom of the tank. So a tank that size probably a medium. I don't remember right off hand how much area they cover but the dimensions are on any website you'd order them from.

Next your gonna want a digital thermometer and hygrometer. Flukers makes a nice combination. Analogs, I and many others have found, are not nearly as accurate as the digital ones.

Good Luck with her!