I keep my hot side around 86-88 as well...
And a background and sides are recommended with baby snakes (gives them a smaller looking enclosure so they don't get stressed as easily) but you don't need them... They do make a tank look nice though so it's up to you, i know they sell 'jungle' stick on backgrounds at PetSmart... Or at least at my PetSmart. Just something to think about, it's in a big roll, they cut off how much you ask for and they sell it by the foot. If i remember correctly, it's pretty cheap
And yes, Het just means it's a hidden trait. So the corn you are buying has normal saddles but if you breed it, you have a chance of having motley babies.
Congrats on your purchase!