I had to do this on one of my sites that had over 3000 pages.
I converted the static pages by spider and by hand to a mysql database.
Next, I wrote php software to serve up the same pages in the same fashion that they were originally served up. Then, I set a RewriteRule in the .htaccess file that would in essense take the identifying info from the original url path and use that to pull the same content from the php/mysql system.
The search engine sees the exact same url it has always seen, but now the page is being served through php, templates and mysql.
Now, when I want to change the layout of my pages, I change one template file instead of 3000 static pages.
All pagerank and
seo value was retained, and I received a system that will let me be a bit more flexible in the future.
It was painful to move the pages from the static to the database, but it has been worth every minute spent doing so in regards to expanded features to share with my visitors.