Customise a checkout page (PHP) repost

Hey, I have a site which uses WP E-Commerce, on the checkout page I need an option to check if you are logged in - If so then show the cart, if not then either create new account or sign in.... Once you are logged in it needs to show your account name and address and access a javascript calendar for booking a delivery time slot. $80 max - Must be completed quickly. Skype or MSN too.... Once the order is completed if needs to add all the details in to the database for WP Ecommerce.... [login to view URL] Go and buy something, then check out...