XSLT replace value

Question

I have an XML like this

Answer 1

Basically you want an identity transform, with override rules.

The following transform

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

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

    <xsl:template match="PrintDollarsAndCents/text()[.='X']">Y</xsl:template>

</xsl:stylesheet>

applied to your input, produces the result:

<OMDefault xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <PrintDollarsAndCents>Y</PrintDollarsAndCents>
   <MailAddrLine1>Add1</MailAddrLine1>
   <MailAddrLine2>Add2</MailAddrLine2>
</OMDefault>

The first template is an identity transform, which copies the input document exactly.

The second template overrides text nodes with a value of X that are children of a PrintDollarsAndCents template. Note that it emits the value Y instead of its actual content.