Checkout this thread I wrote on PVC caging, it should answer most of your questions:

http://ball-pythons.net/forums/showt...With-Pictures!

To answer a few of your questions:

1. You want about 1 square foot of floor space in the cage per foot of snake

2. Either or both will work, I cover both in detail in the thread I linked to above. I would suggest a heat panel for you

3. I don't use this brand, but I do use PVC cage (I prefer Animal Plastics cages)

4. The Herpstat tine of thermostats currently have the most features and are the safest.

5. if you are referring to the acu-rite (pictured below) then you can order them on Amazon or at Walmart

6. I start out my little guys in a 24 x 24 x 12 inch cage (L x W x H) as long as you have good hides there shouldn't be any problems