Good way to selectively merge XML docs?

Hi folks,

I'm interested in merging two xml docs together. The documents use the same
structure, and in the case of similar nodes I'd like to keep the "newer"
one. I'll explain what I mean by that below.

For instance, if I have two docs like so:

<!--xmldoc1-->

<topnode>
<automobilepart>
<name>Radiator</name>
<version>4</version>
</automobilepart>
<automobilepart>
<name>Head Gasket</name>
<version>8</version>
</automobilepart>
</topnode>


<!--xmldoc2-->

<topnode>
<automobilepart>
<name>Radiator</name>
<version>6</version> <!--note newer version from above-->
</automobilepart>
<automobilepart>
<name>Spark Plug</name>
<version>4</version>
</automobilepart>
</topnode>

I'd like to create a document which is a combination of the two inputs, but
only has the "latest" version of a given autopart. In the example above, my
final document would contain a Head Gasket, a Spark Plug, and a Radiator,
whose "version" is 6. How might I tackle this? Could I do it with XSLT?
I'm using the MSXML3 parser to create the first two documents, if that helps
any.

TIA,

-Jim

Jim Bancroft