Customise WordPress Plug-In

Research existing WordPress plug-ins and/or modify to create a plug in suited to our weblog (WordPress 2.5.x). We need a smart contact form (or form builder plug in) to embed a Contact Form into our WordPress pages to enable readers to select and reserve a place in the events outlined in our various Weblog pages and then (after registering their interest on the Contact Form for particular event times and event date) to be directed to Paypal to make payment for attending that event.