Hi!
Some book recommendations:
J2EE Web Services by Richard Monson-Haefel - it is slightly old, but a good place to start and most parts of it are still useful for those aspiring for SCDJWS 5.
Java Web Services Up and Running - One of the few newer books on Java SOAP web services.
RESTful Java Web Services
I recommend starting with learning XML. PLay around with it until you have a firm grasp of the different concepts. After that, SOAP and WSDL will be easier.
Best wishes!
I'm studing for WS certification too and maybe my "study guide plan" could help you:
1. Read J2EE™ Web Services By Richard Monson-Haefel book.
2. Read Java Web Services: Up and Running book.
3. Well read Mikalai Zaikin guide pdf.
4. Take Mikalai Zaikin Mocks.
5. Take SUN mocks.
I've been read a lot of post here in forun, and I realised that many people passed with less effort ! So I believed that is enough !!
Regards