Convert My Site to Wordpress (May Need Custom Template)

I have an existing, nicely-built website that I would like to convert to Wordpress while still keeping the functionality and design. The provider can use an existing Wordpress theme if the finished product looks very close to our existing design or decide if they custom template needs to be created. For example, I would like to have the same header and footer as on the existing site, a menu utilizing the existing design elements, a place to capture email addresses with custom design elements as shown, a place to display our results as shown and a place to show our Twitter feed again as shown. We love our existing design but it's not easy for us to do major updates, like changing pages or graphics, and we have no content management system with the current site. I'm extremely familiar with Wordpress and I'd like to take advantage of its strengths. I would do this project myself, but I'm not a great designer and I'm not sure if design skills are needed for this project anyway. And I don't have time to figure it out. To bid on this job, please view our site ([login to view URL]) and tell me if you think we'd need a custom Wordpress template or not, pricing, and a timeline. Thank you!