SOAPui addresses getting a service up and running through WSDL - but there are two parts - the communications and the content.
The other big challenge is agreeing exactly what the transactions look like and documenting that, in and out, in a standard way that can be shared using HTML and XML.
Fortunately there's a tool available that does all that and also supports integration as a full testing services that allows validation of actual transaction content exchanges, transformations (xslt) and including use of context variables.
Would be great to offer that plug-in (jCAM). This is available on SourceForge as open source - and implements the public OASIS CAM standard for transaction validation. It also uses Eclipse and supports the Java API.
Suspect level of effort to do this is really small - probably less than one day to get it working and package it. I've already done this successfully with OrionSMG's OSS transport engine.
See http://www.jcam.org.uk for more information on API and packaging (jCAM also is using Maven).