C: extending text search: from where to start

I'd like to extend full text search so that I can transform tvectors
in tquery and have direct access to a tvector as a record/array.

I'm on Debian.

This is my first experience with pg source code.
I'd appreciate any pointer that will quickly put me on the right
track.

thanks

--
Ivan Sergio Borgonovo
http://www.webthatworks.it