Hello, you can use the CSV feature, use the sample CSV and add two column named package_id and alive_days .
these two columns will assign the package_id (previously created) and the alive days for the listing in that package. You can see the id of the package going in Geodirectory/Prices and Payments and then in the Prices Tab.
To assign a listing to an author, first create an user (or let him register to the website) then note the ID going in Users – All users, hover with your mouse to the Edit link, under your desired user and you’ll see the address with a similar url (http://yourdomain/wp-admin/user-edit.php?user_id=2), in this example the user id is 2 (admin is always 1).
Insert this ID in the cvs, in the column “post_author”.
To change expire date to a preexistent listing, you can do that via phpmyadmin (or manually via backend, but you knew that already), there is n fastest way. In phmyadmin check the table named wp_geodir_gd_place_detail (if your post type is “gd_place) and you will see a column named expire_date, foremother update your new date in the format YYYY-MM-DD