Your code is getting the Field node with the name attribute equal to "Id". You can change the XPath expression to get the element text within the Value node of the element where the name attribute is "Id". So the XPath expression should be:
//Field[@Name=\"id\"]/Value/text()
Then change the code in the for-loop to
Node currentItem = nl.item(i);
System.out.println(currentItem.getNodeValue());