I believe you will have to edit the search.php file in the currently active theme directory for that, as that is the one that’s invoked when WordPress passes the results. I believe it’s not possible to simply bypass the search results to a different page, I’m almost sure they will be overridden with the default page content.
To change the URL of the search page, you will have to use .htaccess rules (or other methods) to resolve the redirections, I beileve this is a good tutorial on how to do that: http://wpengineer.com/2258/change-the-search-url-of-wordpress/
Once the desired redirection works, you can change the redirection in options in ajax search pro to the same URL and pattern.
In this case, still the search.php file in the theme directory will handle the layout, but will be ‘covered’ under a different URL, as a page.
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