I am from kottayam in kerala. I got married six months back.I want to change my wife's surname.is it enough that I publish in the gazette.how do I do it.do I have to get the form from govt press in trivandrum and submit it there.or is there any provision to do it from kottayam itself

You can do it by publishing the name but there are other rules also. Here is the official word on it.

--:: Kerala Gazette - Published by Authority ::-- (http://www.egazette.kerala.gov.in/forms.htm)