Parsing XML and then sending via SOAP

I’m looking to write a small test stub that will read in some XML from a
document, and then send it wrapped up in a SOAP envelope. I’ve found the
XML.com documentation useful

http://www.xml.com/pub/a/2005/11/09/rexml-processing-xml-in-ruby.html

but haven’t really worked out whether I can do the following:

Read the document in as a File
create an REXML document file handle
send that file handle wrapped in a soap envelope

?

If so, has anyone got some good documentation on constructing and
sending out XML via SOAP? I’ve played about before with the SOAP calls
to Google/Yahoo/Amazon etc. but not tried wrapping up ML and sending it
before…

Even some short examples would be much appreciated.