Thanks for your help – this is definitely in the right direction.
Could you help me out with the actual tags I need to change / where they are used?
add_action( 'add_meta_boxes', 'change_tag_meta_box', 0 );
function change_tag_meta_box() {
global $wp_meta_boxes;
unset( $wp_meta_boxes['post']['side']['core']['tagsdiv-post_tag'] );
add_meta_box('tagsdiv-post_tag',
__('City'),
'post_tags_meta_box',
'post',
'side',
'low');
}
This shows how to change tags in general – where are they used in the plugin files for the custom post type?