I think you should try to find a solution that keeps the informational pages as they are now, because they are such a big part of the site and most likely a major support for the ecommerce pages. Also, the possiblilities that have been mentioned would involve a big re-vamp, which in my opinion should always be avoided except in drastic situations.
So I think you should look at the possibility of creating some new unique content to add to the ecommerce pages, while leaving the informational pages unchanged. This would probably involve more work than the other approaches, but in my opinion would have the best chance for success. As an alternative, which would be less work, you could just move part of the content of the informational pages to the ecommerce pages, perhaps with some re-writing and mixing.
P.S. As an added note, I don't think Google puts as much trust in sites that have a lot of re-directs and/or deleted pages.