how do update products, information & prices from remote website?

Hi,

Can someone please tell me how to update products, product information and prices from a a remote website?

The remote website runs on ASPX and they provide an XML feed, but with all the products.
The XML feed has, at this stage there’s 18531 products in the XML feed, as example:

<Product>
    <ItemCode>11-113</ItemCode>
    <Name>Trolley Bag</Name>
    <Description>Holds most 17" laptops. Main zippered compartment is spacious enough for an overnight trip.</Description>
    <Price>1399.99</Price>
    <Flags>0</Flags>
    <BaseItemCode>11-113</BaseItemCode>
    <Id>cf3988f0-12b3-4dc8-8112-cccd29d9206a</Id>
    <Size />
    <Colour />
    <Promotion>0</Promotion>
    <StockCheckCode>11-113</StockCheckCode>
  </Product>