To create a page in the cms have alook at the 'SiteTree' and 'SiteTree_Live' tables.
I think you would be able to get it to work by doing something like 'INSERT INTO SiteTree (Title, Content, URLSegment, ParentID....) VALUES ('My Page', 'My Content', 'page-url', 0)
It would involve just a bit of trial and error and playing round :). I think you will be able to just insert into sitetree and then run publish/all rather then insert into 2 tables.
Also another way that might be useful is andy has developed a static importer for one of our clients sites, imports a couple thousand pages from a think a CSV file export of their database. You might like to check out the code for that - http://open.silverstripe.com/browser/modules/staticimporter/trunk