I have written a detailed article at Javalobby which provides step by step instructions on how to write functional tests for your web services using SoapUI.
Here are the links where you can find the article on various Zones at Javalobby:
1. Java Zone
2. Architects Zone
3. SOA Zone
The next part in this article will cover SoapUI and Groovy.
Give me a yell if you need any help.