Transfering entire site into WP

I have had a site up for over four years. It consists mostly of columns written by a variety of authors. Some of these columns are Q&A columns that allow reader input. This commenting has always been done manually. (Readers email comments, I post them in the appropriate articles.)

I’d like to bring my site up-to-date by automating this through WP. I’d like to transfer all the old articles into WP, allowing readers to comment at will.

Is there a way for me to post the articles under the appropriate author’s name, then add the comments, while somehow backdating them appropriately? (I don’t want all the dates to read January 2007.)

FWIW, I’m trying to integrate WP with my existing Vanilla forum, so that all the comments on the blog go to Vanilla.

The site is http://www.mormonmomma.com

Any help much appreciated.