[Michael P]

1) No, you only need to login once.
2) You can check the "can users views ads" permissions for each usergroup in the Admin Usergroups page to prevent groups from viewing ads.

If you want to keep unregistered users out of the entire section, that would require a small mod to check permissions on the main index similiar to the checks done in showcat or showproduct which deny access to people without it.