I would like to add some custom product fields to the advanced search page. For example, I have fields 'products_volts' and 'products_watts' that are part of my database.

These are apparently the relevant files:
includes/languages/english/MYTEMPLATE/advanced_search_result.php
includes/languages/english/advanced_search.php
includes/templates/MYTEMPLATE/templates/tpl_advanced_search_default.php
includes/templates/MYTEMPLATE/templates/tpl_advanced_search_result.php

The first two define the text, and the third one lays out the search page, and the last one executes the queries. That's my hunch. Beyond that I'm stuck. Can someone provide some direction here?