<xsl:for-each select="ExportEntries">
        <xsl:if test="../Restore/@state = 'True'">
                <xsl:for-each select="ExportEntry/Field">

This works as I want, but to me it doesn't seem to be the best way.
Is there a better way to do that kind of check?  I want to restrict
it to the "ExportEntries" node first, as there are only a limited
number of times that that node will exist, and the "Restore state"
node is often there for other things, so I think I'm being more
efficient doing it this way.  Am I doing this right?

You use a predicate to achieve this:

  <xsl:for-each select="ExportEntries[../Restore/@state='True']/
                        ExportEntry/Field">
    ...
  </xsl:for-each>

I hope this helps.

Cheers,
Nick