Develop custom Magento extension

We got an extension that is adding a fee to an order, if a particular payment method is selected (adds a payment fee). This works well, but we now need to extend this extension to also do the following: * After the customer has pressed the "Submit order" button, the fee should be removed from the order, and instead a new product should be added to the order. This is a static product (so same product every time) * The order should then be stored in Magento and processed as normal. * In back-end, under the settings for each payment method, it should be possible to select what product to add to the order, if the given payment method is selected. You bid should include completion of the extension and fulfilled in a way so it can be uploaded and installed through Magento Connect. The extension should be compatible with Magento 1.6 and 1.7. You must follow our guidelines for developing Magento extensions (basically just say something about naming conventions, etc.). We are in a hurry with this project, so please only bid on it if you can start right away and complete it within a couple of days.