There are several parts to this:
- Need a link that says "Change Item" similar to the Delete link on the Basket page. This link would appear in the Basket (Basket.aspx), Item Details (One Page Checkout) or confirmation (multi page checkout - ShipMethod and Payment) pages.
- Clicking the link should take you to the item and when the item is saved, replace the current basket item with the new addition. Instead of an Add to Cart button, the product should probably display a Replace in Cart button to be clear to the customer.
- When the user clicks on "Change Item" and it takes you to the item, it should preselect the options the user has already picked for the item in the basket.