XML assist

I feel pretty stupid not being able to accomplish this but wanted to see if anyone on here can assist with some sample code that works.

I have an XML file that contains,

     <server>
        <name>myserver</name>
        <displayName>myserver</displayName>
        <comment />
        <logonCredentials inherit="FromParent" />
        <connectionSettings inherit="FromParent" />
        <gatewaySettings inherit="FromParent" />
        <remoteDesktop inherit="FromParent" />
        <localResources inherit="FromParent" />
        <securitySettings inherit="FromParent" />
        <displaySettings inherit="FromParent" />
      </server>

I want to run Powershell against this file and uppercase the values on the <name> and the <displayName> nodes and then save the file.

Have tried multiple samples from the cloud and just cannot seem to make it happen.