Add Additional Checkout Step - Magento

I need to add an additional step to my check out in magento. this magento install has two sites associated with it so will need this programming to be for one of the sites only. the additional step will require the user to enter the date and time of the delivery, and answer a few additional questions. Also allows the user to add a comment. So the additional Step will include the following questions (all are required fields): 1) Calendar (unavailable depending on the type of delivery chosen), 2) Clock to enter time (unavailable depending on the type of delivery chosen), 3) Confirm if they want there products frozen before delivery, 4) That they have read the terms and conditions 5) Return Deposit.( to which a fee is to be added to the bill)