Payment Processor and Contol Panel for Existing Site

I want payment processor installed and configured on my site so that the members can pay for the services available at my web site. My web site is developed in ASP. I also want to develop a Control Panel on my website which will help me administrate the entire web site, including manipulating members, payment reports, sending e-mails, event management, offers and promotions, advertising options etc. The control panel must be compatible with existing pages and functionality. Previous experience on Payment Processor/Control Panel development is highly preferred. Will provide payment processing details to the winner. Thanks.