ebay checkout

We need an checkout process, to do a few specific requirements and should work as follows. 1. After our ebay auction ends an automated email will be sent to the winning buyer advising the total. (using our existing selling manager pro) 2. In the automated email will be a link to a checkout, which the buyer will select if they have finished purchasing items from us. 3. If the buyer has only purchased one item, they will see the total amount due, and all our bank/postal details. There will also be a field where they must enter there postal details for where the item is to be sent. 4. If the buyer has purchased multiple items, within a time frame (set by me) the buyer will use the checkout after they have purchased the final item. The checkout process will recognise the nultiple items (bought within the time frame) and will give a postage discount as follows, the item with the highest postage rate, full charge, all subsequent items 50% postage rates. 5. We have just got our own phone order merchant facility, and we need to provide a secure email link for the buyer send us there credit card details. So possibly this could be incorporated into the checkout page or a link be placed to a secure page??? 6. After the checkout is complete, we can view the checkout and choose to print an invoice. The invoice will show the transaction details, buyers details and must break down the total amount to show 10% GST. 7. There needs to be a blank field for each transaction, where we can enter a parcel tracking number for our reference, manually, or in the near future using a barcode scanner. I hope someone can help me with this, it will make our job alot easier. We want this to be a simple as possible and all the sale details from ebay would be imported into the checkout automatically, and the buyer should not be allowed to edit any amounts. Look forward to your response.