A MailChimp Opt-In and two other fixes

Hi, Looking for talented Joomla wizards out there for the following: a) When my site loads, I want an Opt-in modal popup box to appear with the ability of visitors to enter their FIRST NAME and EMAIL and then "Subscribe". This input data must link to our Mailchimp account to a specific list that we have created. We want our mailing database/list to be managed through mailchimp, not Joomla. I already have a mockup of how I want the opt-in box to look. I want to the ability to change the content of the model box if I desire. Look forward to working with someone on this. It shouldn't take long to do this. Thank you