Yep sounds pretty right to me, good luck with your Corn snake! I would love to see pictures once you get him/her xD
Also, you can just use either the UTH or the heat lamp since you'll be using paper towels. I would recommend paper towels for a plastic tub because it's easier for the heat from the UTH to get to the top of the substrate. So, if you can get the temps at the correct level with a heat lamp then that is all you will pretty much need.