Should be no problem to complete, I have done several custom captcha methods, as well as extensive experience in php and webserver security issues, for high performance, high traffic applications. Search feature should be relatively easy, especially if mysql database already has fulltext index. Also, have done some extensive work with a couple of classifieds scripts, paypal IPN and Checkout methods (including express checkout) provided sufficient access is provided, I could have this done in 5 days or so.