Invoking webservice and diplaying the response in form/xhtml

Hi,
Can any one help me in to achieve this?
when a page loads it should prepoulated with valuew from a webservice call response
then these values are editable and once i press change data button it should call another webservice and
update the change and a confirmation page should be shown.

1. how to invoke webservice and show the response in form?
2. how to submit the form values back to xpl/then pass to webservice?
3. after this, based on the response (success/failure) how ot decide and show the success/error screen?

Please help.
Thanks in advance...