You don't have to use the db database handler to access the vb database. With just the username/password you can use php's mysql_connect() // mysql_query to do the trick. If you want to use the vb config,
require_once('vb_forum/includes/config.php');
For 1, assuming you only want to show members with avatars and assuming you have avatars in the filesystem:
You must first be a
registered member to view any code.
Naturally you can format the output however you want.
usergroupid is the usergroup you want to use.
Similar for 2, but add ORDER BY RAND() LIMIT 1 to pick a random one. Also LEFT JOIN userfield USING (userid) and add the fields you want to the select range.
I know this is a bit of a throwtogether but it should get you started - it depends how much you know about mysql in general.