Hi,
Have a read through the caresheet before you go shopping.
I'd pick up some of the aquarium backing Silver Demon mentioned to black out the sides and back of the tank with at the pet store. But everything else you need can be bought cheaper elsewhere.
Hides I would probably try and buy those saucers they sell for catching drips form plant pots and cut a single opening in them from rim to base and turn them upside down. Very inexpensive, easy to clean and ideal from the snakes point of view.
You can also pick up the foil tape in lowes etc that will hold the heatmat on the underside of the tank.
I would recommend a thermostat rather than a rtheostat though unless your house temps are extremely stable.
I would also recommend newspaper or paper towels for the substrate ( easier to clean and much easier to keep an eye out for things like mites, unusual faeces etc ).
dr del