There may be a better way to do this (the xml spec defines a renameNode method, but as far as I can tell MS hasn’t implemented this, and if they have I couldn’t find it), but this sufficed for my purposes.  This just creates a new node under the parent of the node you’re looking for and then copies the original nodes’ text content into the new node.  It then removes the original node. 

[xml]$xmlDoc = Get-Content c:\XMLFile.xml

foreach($node in $xmlDoc.SelectNodes('/Node1/Node2')){
	$newNode = $xmlDoc.CreateNode([System.Xml.XmlNodeType]::Element, $node.Prefix, 'NewNode', $node.NamespaceURI);
	$newNode.InnerText = $node.InnerText;
	$node.ParentNode.AppendChild($newNode);
	$node.ParentNode.RemoveChild($node);
	
}
$xmlDoc.Save('c:\XMLFileReplaced.xml');