I just made my first cake with fondant and it actually turned out really well. Now I am wondering, do I have to put it in the fridge if im delivering it tomorrow. Eggs and milk were used in it, so im thinking it needs to be in the fridge. But i've heard that putting your fondant covered cake in the fridge will ruin the fondant. What do I do??

Unless it's horribly warm in the area you're storing the cake OR if you used a perishable filling, there's no need to put it in the fridge. The eggs and milk in the cake are rendered stable by the baking process.

Box it up, but don't seal it airtight (like in one of those plastic cake carriers). If air can't circulate the fondant will go goopy. It'll be just fine for delivery tomorrow.