What is the easiest way to clone a webservice?
get a hold of the WSDL and any associated XSDs and use WSDL.exe to generate the classes and add them to a webservice project.
"Our clone will need to output sample data, but use their exact method calls and types."
So it's maybe enough to record the original webservice data and play it back?
As startpoint, Fiddler with Autoresponse may help. As advanced solution your partner is SOAPUI.
(source: soapui.org)