oscommerce selectable products payment options custom item

Hi, Im looking to do a mod on a oscommerce script just for doing the following: in the admin side There must be an option to select which payment options will be available for the products, so since we already have the cash option some items needs to be like preordered so, they need to be payed in advance, so for these items we need that the customer make the payment throught paypal, dineromail or mercadopago. Also there must an option to select if this is a common item so only the payment method is defined or if its a custom item, if its a custom item some options will need to be added CUSTOM PRODUCT -> Also these products must be attached to the member account or add to the customer (for each product) a section in their account page so the customer could visit it to retrieve that purchased product (these products will be only an img file, pdf, or something like that, not big files) so if the customer lost the purchased item email he could retrieve it from her account. This thing must be editable from the order editor in the admin panel so this is not defined by the product is defined per each purachased item by the order, this means that the product will not have the same image file for all, it will change for every new order so thats why we need to add a custom image for each order. So in resume, if the order contains one of these "custom products" in the other editor must be an option to attach a file, also there must be a field to put in some text, and also there must be another field that will be the email text that will be sent after completed all the other things (THIS WILL BE FOR EACH CUSTOM PRODUCT IN THE ORDER also if the order containts 2 or more qty for each custom product these things must be defined one by one). Also these products when purchased must send and additional email with a "in process" message or something like that, since the sending process is manually performed by us ,in a file that must be editable from the admin side, and also in the customer account, there must be a box with these custom purchased items and the information that we added from the admin side. Hope its clear! If there is any doubt just ask Best Regards