If you have the WCF Rest Starter Kit preview installed, there's a neat trick:
- open Visual Studio
- select your XML node contents (the XML that makes up one of your nodes) and copy it to the clipboard
- from your "Edit" menu in Visual Studio, pick "Paste XML as Types"
This will paste your XML that's on the clipboard into your project as a C# class that is capable of deserializing that exact XML. Pretty nifty!
See these blog posts about it:
That should save you a lot of typing and make life a lot easier!
UPDATE:
OK, you already have your classes generated from the XML you get back. Now you need to convert a XmlNode to your class.
You'll have to do something like this:
private static T ConvertNode<T>(XmlNode node) where T: class
{
    MemoryStream stm = new MemoryStream();
    StreamWriter stw = new StreamWriter(stm);
    stw.Write(node.OuterXml);
    stw.Flush();
    stm.Position = 0;
    XmlSerializer ser = new XmlSerializer(typeof(T));
    T result = (ser.Deserialize(stm) as T);
    return result;
}
You need to write the XML representation (property .OuterXml) of the XmlNode to a stream (here a MemoryStream) and then use the XmlSerializer to serialize back the object from that stream.
You can do it with the generic method and call 
 Customer myCustomer = ConvertNode<Customer>(xmlNode);
or you could even turn that code into either an extension method on the XmlNode class so you could write:
 Customer myCustomer = xmlNode.ConvertNode<Customer>();
Marc