Eclipse plugins for easing web service (and any other J2EE component) development already exist: see the WTP project.
We have plans to add web service invocation/publication capabilities to the core jBPM. GPD support that leveraged WTP features would follow. This is a matter of time and community demand. If you're interested, file a JIRA issue and vote for it.
You can find detailed information about deploying BPEL processes in the user guide. It resides in directory doc/userguide/en/html of the jBPM BPEL distribution. A quick summary:
Write your BPEL, interface WSDL and XML Schema documents
Pack your documents in a process archive
Deploy this archive to your database
Generate the WSDL implementation documents (servicegen tool)
Generate the WS4J2EE server artifacts (wscompile tool)
Write the web service deployment descriptors
Deploy the web application to your app server
You can edit XML Schema and WSDL documents using WTP tools. The BPEL document has to be written by hand or an external editor. The Oracle BPEL designer is nice, but be aware of the following license term when you download it:
We grant you a [...] license to use the programs only for the purpose of developing a single prototype of your application
Enjoy the ride ;-)