glad you choose a cornsnake :) there very sweet and kind if they get to know you. i would suggest to get him/her as a juvenile though. they'll be more tamed
as for feeding they should eat on there own, if you get a baby/hatchling you'll have to feed them pinkies, insects aren't in there food chain so don't try it. and if you choose to feed frozen (frozen foods are cheaper than live) you'll have to get warm/hot water, let it boil, and when it looks thaw grab it and squish it, make sure it isn't frozen inside (so it won't get the snake sick) and it is warm since they notice prey by heat mostly. if you have to feed pinkies, don't leave the pinky in for a long time or the skin will break and it would get digusting ;p
flooring you could buy at many petstores, never use sand. you could even use newspaper (i wouldn't suggest it if you want it to look nice, lol) and be careful with getting gravel you want to make sure it is safe. i don't know the names of any though XP and the thing why WE use newspaper because we don't want get the snakes mite's sometimes there in the dirt sometimes there not, with our luck there in there -.-" and simple to get rid of mites, let them bathe in water, in there water bowl, any where were there isn't chemicals to hurt them. the way to notice it when you see either on the body or (mostly) on top of the head it would be white cracks between the scales, and the snake mostly stays in the water bowl.
make sure they don't bathe too much because they could get scale rot, but that's a rare case, out of 1 out of 10 snakes get it.
from experience with pythons, there also sweet, kind, and very intelligent :) "Melissa" our normal ball python, when they had mites and she would share a big tank with another ball (younger than her) was a yellow belly ball python "Teo" and he wouldn't go to the water bowl, but melissa will bathe in it and go on top of teo and let him soak ;p sadly he passed away.
after feeding DON'T TOUCH THEM unless your putting back into the tank CAREFULLY. the reason why is because there digesting, and when they crawl all over you hands/fingers, it will make them either regurgitate, or mess up there digestive system