Programming :: Updating XML Files Using A Shell Script?

I continue to work on automating the update and deployment of a vendors WAR files, and have bumped into my next challenge... The vendor provides web.xml files have entries that look like this

Code:

<context-param>
<param-name>siteminder.enabled</param-name>
<param-value>false</param-value>
</context-param>

I need to search the file for a param-name and replace the param-value below it with the correct value. I expect sed or awk is the trick on this, but I am not sure how to have it search for one line, and have it update the line below it.