Add mailchimp integration to a custom plugin

we want to add mailchimp integration to a plugin we are developing, you can view the plugin in action at [login to view URL] we want to be able to have the user specify from the admin area-settings area- integration area of our plugin their mailchimp api key and list id so when a subscriber enters their email and name on our contact form this information is added to a list in mailchimp. this is very similar to what the contact from 7 extension does (hint) Please let me know how long it will take you to complete the project. Thank You