Customizing Themes for Complex Graphic Designs

Hi, I’m a novice with WordPress. I’ve been asked to build a site for a relative, who paired me with a graphic designer that she knows.

The site she’s asking for is structurally pretty simple, as in the number of pages and the general layout. She also said she liked another site that uses Twenty Eleven, so I was thinking with starting with that or another basic WP theme as a template and just making some tweaks for design and functionality as needed.

The designer though, has ideas for complex designs that I’m not sure I can code in the time that I have to build the site. One page he wants to add is a huge graphic (that unless I can get in image files would probably require a lot of CSS) with sections that pop out when you hover or click on them. Another page would have a display of reports that also pop out and open when you click on them. I want to include these, but I’m not sure how I would incorporate them into the site, or if it would even make sense to try to customize a theme like Twenty Eleven to include them.

So my questions are:

1) Am I off track thinking the best way to approach this is to start with a simple theme like Twenty Eleven and try to customize it? Or would it be better to try to look for a premium theme that might support this? Or start from scratch?

2) Does it make sense to ask for designs as images so that they can be added without writing a lot of custom CSS, or is this generally a bad approach?

Please let me know your thoughts. Thanks!