If you haven't checked out the care sheet on this site please do it is a really good one.

You may need both. Make sure you have a good thermometer and a way of controlling the heat mat. If you can swing it I highly recommend using a good thermostat (I use a herpstat).

You need 90-92 on the hot side surface and 78-80 on cool. Ambient should be between 80-85. Humidity between 50-60. It is very important o have it setup for a week or so to make sure you have consistent temps and humidity. I am not an expert but it is easier in you and the snake if you have everything ready. It may take a little playing around.

Good luck.