Small changes to source XML

Forgive me for seeming ignorant, but I certainly am in this case.  I want to
mostly copy all of my source XML to the output XML, with some small changes.
For instance:

<root>
        <a ID="74">
        <a ID="75">
        <a ID="76">
</root>

I want this output:

<root>
        <a ID="0">
        <a ID="0">
        <a ID="0">
</root>


What is the best way to do this with a lot of XML without using xsl:element?