PrestaShop info converter

Hello, We are building an e-commerce site with PrestaShop. Site will sell books. We did join a service that supplies current booklist in our country. Booklist is in XML format and containts a unique id specific to supplier, book name, writer, isbn number and other important informations. We need a php script to convert this xml and import to our prestaShop site using Web Service API of presteShop. We also want to check previously imported products and if there is an update, we want this script to update.