Create and install a Shipping & Order Editing module for an Oscommerce 2.3.1 installation

We have an already working OScommerce 2.3.1 installation. I need a shipping module that will charge First item a certain amount and every extra item little more amount. Tax should be added to the shipping fee at the last stage. The freight amounts should be able to be inputed from admin. Three Zones within the same country (A field for Zone needs to be added to the [login to view URL] file) will have 3 different freight charges. --------------------------------------------------------- Order Editing Module will allow all Order fields to be edited. Ex: If someone wants to change the product or if we want to edit the price after order is placed. Please note that its a OScommerce 2.3.1 installation. Ask, if you have any queries.