[jQuery] selecting node values in XML

[perikut]

hi everybody,
I want to change the values of an XML node (if another ajax result is
successful).
I'm not sure how to access these values (and if found, execute
something).
If I visualize this xml in localhost (http://localhost/example.xml),
should I be able to apply and visualize the results of these
selectors? (firebug returns allways [null] when I use only it: $
("Name:contains('XX')"), and it should also work for XMLs, right?)

Thanks!!
...
success: function (j)
  {
    url="world.xml";
    $.get(url, function(xml)
    {
                                                   $
(xml).find('Name[childNodes[0].firstChild.text]=="XX"').function(){
          var item_text = $(this).text();
          config.objects.mainMap,'//wmc:Name',item_text
});

A simple XML:
<LayerList>
  <Layer>
    <others>uuuii</others>
    <Name>XX</Name>
  <Layer>
  <Layer>
    <others>uuuii</others>
    <Name>YY</Name>
  <Layer>
<LayerList>