Renaming XML nodes and replacing values with XSL

I am having a problem where nothing is being replaced.

I looked at other SO issues to rename nodes and to replace values, and have copied the examples from the answers, but nothing is working for me. I suspect that I have something subtly wrong, but I have reviewed my C#, XML, and XSL code, and can't seem to find it.

Here is my C# code:

private static string GetOutput(string xmlFileName, string xslFileName)
{
    var xmlDocument = new XmlDocument();
    xmlDocument.Load(xmlFileName);

    var xslTransform = new XslCompiledTransform();
    xslTransform.Load(xslFileName);

    var stream = new MemoryStream();
    xslTransform.Transform(xmlDocument, null, stream);

    stream.Position = 1;
    var reader = new StreamReader(stream);
    string output = reader.ReadToEnd();

    return output;
}

Here is my the contents of my XML file:

<?xml version="1.0" encoding="utf-8" ?>
<TransformThis xmlns="http://schemas.datacontract.org/2004/07/TransformTest" 
             xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
    <f_name>John</f_name>
    <l_name>D&apos;Oh!</l_name>
    <Version>1.0</Version>
</TransformThis>

And here is the contents of my XSL file:

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
                xmlns:msxsl="urn:schemas-microsoft-com:xslt" 
                exclude-result-prefixes="msxsl">

    <xsl:output method="xml" indent="yes"/>

    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="Version/text()[.='1.0']">1.1</xsl:template>

    <xsl:template match="f_name">
        <FirstName>
            <xsl:apply-templates select="node()|@*"/>
        </FirstName>
    </xsl:template>

    <xsl:template match="l_name">
        <LastName>
            <xsl:apply-templates select="node()|@*"/>
        </LastName>
    </xsl:template>

</xsl:stylesheet>

When I run my program, the output is the same as the original XML. Neither the f_name and l_name nodes have been renamed, nor has the Version node value been replaced.

Any help would be greatly appreciated.

UPDATE Per michael.hor257k's answer below, I have modified my XLS file as follows:

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" 
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
                xmlns:tx="http://schemas.datacontract.org/2004/07/TransformTest"
                xmlns:msxsl="urn:schemas-microsoft-com:xslt" 
                exclude-result-prefixes="msxsl">

    <xsl:output method="xml" indent="yes"/>

    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="tx:Version/text()[.='1.0']">1.1</xsl:template>

    <xsl:template match="tx:f_name">
        <FirstName>
            <xsl:apply-templates select="node()|@*"/>
        </FirstName>
    </xsl:template>

    <xsl:template match="tx:l_name">
        <LastName>
            <xsl:apply-templates select="node()|@*"/>
        </LastName>
    </xsl:template>

</xsl:stylesheet>

I added the ...TransformTest namespace to the XLS file, and prefixed the match nodes with tx:.

Now the transformation is working, but it is also added the tx: namespace to the renamed nodes:

<?xml version="1.0" encoding="utf-8"?>
<Transformer xmlns="http://schemas.datacontract.org/2004/07/TransformTest" 
             xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
    <FirstName xmlns="" xmlns:tx="http://schemas.datacontract.org/2004/07/TransformTest">John</FirstName>
    <LastName xmlns="" xmlns:tx="http://schemas.datacontract.org/2004/07/TransformTest">Doh</LastName>
    <Version>1.1</Version>
</Transformer>

Also, when the XML is deserialized into an object, the LastName and FirstName properties are null, which I suspect has something to do with the additional namespace attributes on those nodes.

I would like the output to look just like the original XML, but with only the names and values changed.

UPDATE #2 michael.hor257k ADDED: an example XLS file in his answer. This resolved all of my issues.