Prestashop Customization

The PHP customization I need right now : - Changing the form that is now used to add a product : You can see it here, login on to the website ( [login to view URL]) with this credentials : /abc123. Go to "Mi cuenta vendedor" ( My seller account) and go into "Productos" ( products) and then "Añadir Nuevo" ( add new) : You now see the current form ( a bit customized by me). It has some tabs ( images, associations, etc etc...) I need the form to be on only one form, without tabs, on one page and with this fields: go into this website [login to view URL] . Log in with this credentials : DarioB/dario2014 , go to "Mi Perfil" and clic the red button "Añadir un producto". You will see the form I want on the other website. As u may see, Im trying to migrate a website from Joomla/Virtuemart to Prestashop. I will need that some fiels appears based on the category the seller choose, etc... I need to validate the form , per example, is needed that the seller add at least one image. And a check box asking if he wants is product to be a "Featured Product". If so, we will charge him some cost. It will be added to the seller invoice. The other customization I need right now is that the system be able to send messages ( emails ) to the seller too. Now is able to send messages to the buyer, but I need that when the order reaches specific status, the system sends an email to the seller with an invoice ( the commission). The mails must be sent too to the seller(s) if there is more than one since it is a multi-cart system. I need some other customizations too, but these are the "bigger".