Needing a bit of help (all advice welcome)

[200xth]

3) Can somebody please just tell me everything is gonna be fine? Hahahah. I want to do this right and I want to give this animal the longest and healthiest life possible, but I am just so stressed about doing this right.

I wouldn't stress too much. As long as you have the setup in decent shape, your snake will be fine. They're pretty tough, so even if you miss on the setup by a bit, you will be able to make adjustments and get it right and your snake will be fine.

Setup the enclosure a few days in advance so you can check the temps and humidity and have everything in place for when you do get the snake.