What should I do with the egg since I don't have an incubator setup?
Also... And I feel horrible asking this... The dark red spot that I mentioned on the egg... Does that face up or down? I tried not to turn the egg but figured it was more than likely infertile... Now that I'm not positive I'm worried I may have turned the egg without thinking about it.
In regards to which way is up, it depends on the egg, so I can't really help you there. Though, if ALL you see is a red spot, signs continue to point to it being a slug rather than a fertile egg.
I wouldn't spend money on an incubator for one egg that is most likely not fertile. Personally, I would just pitch it.
If you really want to see if it will hatch, you can put the egg in a plastic container with a mildly damp (not wet!) medium, cover it with a damp paper towel, close the lid (no air holes) and put it someplace warm where it won't be bothered (like a closet shelf). Refresh the inside air by opening and re-sealing the lid every week or so, and spritz a little more water if the paper towel gets dry. It will be a long incubation period this way, if it's even going to hatch at all, but it is an actual incubation method.
ETA: You should also seriously consider asking these sorts of questions on the cornsnake forum, as well. Nothing against Chaz, but the cornsnake folks are very well equipped to answer cornsnake questions.