I upgraded my website to D6 to D7 successful but only with the development version (not in production) and I've new datas in production since (Drupal 6). So I'm wondering the best way for update the Drupal 6 database to the Drupal 7 database.
You could migrate DB data with the Migrate module (though it's not very light module and has an individual learning curve, so if you are not a programmer, or not yet, it might be better for you to find a Drupal programmer that will help you run it). Otherwise, if the site is small (i.e has only several or about fifteen pages) I would suggest of building it from the start... In most cases it shouldn't take much time..