Contact Form Integration in my site

hi i want to add a contact form in my wordpress site. i need to capture leads from my site. there is all ready a form created in web site and it works fine. i need to make some changes in that. as i want every filled up details from all listing will be delivered to my mail as well as listing owners mail. need a popup when a visitor search for any category a popup will be there demanding for their information and send that lead again to my email.