^^^^
Yes, you can bring food and drink in (as long as it's not in a cooler, etc. of course)
You can buy a refillable mug. This year's mug is $15 and refills are .99. Probably not worth it for one day. If you do happen to have a mug from past years, refills are $2.99. There are several places to eat and the food is really not bad. There is one place that sells footlong corndogs and fries for $6.99, hamburgers/fries at another for around the same price. Pretty standard for theme parks. They do have a bigger variety of food, though than most places. Fajitas, taco salads, polish sausage, etc. and get a funnel cake! Yummy!
There is plenty to do to spend a whole day. There are 3 major roller coasters and a new thrill ride, Barnstormer that are all good if you like that kind of thing. There are several shows if that's more what you like. There's also a kiddie area/ Country Fair that has lots of rides. There are water rides, too. I think you will be pleasantly surprised how much there is and how clean and nice it is. Of course it's no Disney, but it still has plenty to offer.