1. it can be a separate database or the same does not matter. In the same database you simply make sure your classifieds has a unique table prefix which on a normal install is cp_
2. the integration uses your
vb users for an integrated one login on the site yes
3. your forum would be say in forums directory and classifieds in the classifieds directory yes but integrated with
vb it uses the
vb login and you can use the
vb header footer and style over our application for the same look