Buying from car max process?

I’m thinking about buying from car max, it says I was pre approved with a certain down payment and monthly payment. But it wants me to pay the shipping cost to get it here then test drive. I don’t mind that but I am worried I am going to get it shipped here and then they deny me for bad credit haha. Does anyone know how set in stone my “pre approval” is? I don’t have bad credit and I work full time so I know I can afford the car but not good credit history and I’ve been denied all day for cars even with a big down payment so it does worry me I’ll spend money shipping a car here just to get denied.