I'm new - here's my ideas for my habitat- can you help?

my idea; I have a  gallon fish tank I will turn into a terrarium so I will turn it on its side so its at 29 inches in height (floor 12x16"). I am hoping to put a kind of tropical  tree-like plant so he can climb (I saw online  -and want- a Dracaena Marginate  - not sure where to get it)  How do you know which plants are good / safe crestie?

also I need to know what kind of heat pad I need.  Should the heat pad cover the whole bottom?  I noticed that there was different kinds of heat pads so what should I pick?  Do I need a larger heat pad because my vivarium is so tall?

also since I have my vivarium standing upright what kind of lid do I need? note: since my vivarium is standing upright my lid would be on the side.

if anyone sees any problems with what I want to do please reply

PLEASE AWNSER WERE DO I GET HEATING PADS FOR CRESTIES!!!