GET, Modify, POST XML from Web Service Requests (Webtests)

Question

I'm using load testing to exercise an API, so I'm creating many small webtests which mimic typical user operations.  One of my operations will be a GET of transaction data and a PUT of that same data, slightly modified.
I'm able to capture the response from the GET in an extraction rule and resubmit to the API, the question is how to manipulate the XML so that there's a small typical edit.   What's the best way to do this?  
I understand the nature of the web test plug-ins, as the "cartilage" around the bones of the webservice requests.  I would much rather angle towards a plugin than convert to a coded test and modify that way.  I like the normal non-coded
test interface but I dont know that the webtest plugin nor webtest request gives me the granularity the coded webtest does.  Unfortunately, I dont like the fact I can't easily debug through the coded webtest.
This seems like a straightforward operation. Do I understand all my options? How would you do this?

Answer 1

On further review, I might have figured this out.  I misunderstood something I read online.  The web test request plug-ins can be associated with an individual service call and aren't automatically applied to all service calls in a web performance
test collection.
.. I can do something like this to access my captured context information and manipulate the XML via XDocument/XElement.   - This demonstrates how to get my captured {{ResponseDocument}} from the extraction rule.
    public class XmlModification : WebTestRequestPlugin
        public override void PreRequest(object sender, PreRequestEventArgs e)
            MessageBox.Show(e.WebTest.Context["ResponseDocument"].ToString());
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