Modify Contextual Help

If you want to remove some or all (default) help tabs, then you could do something like this inside your function.

$current_screen = get_current_screen();

$white_list = array(
  'overview-link', // If you want to keep default some tab title and content
);
if ( $current_tabs = $current_screen->get_help_tabs() ) {
  foreach ($current_tabs as $tab_key => $tab_config) {
    if ( ! in_array( $tab_key, $white_list ) ) {
      $current_screen->remove_help_tab($tab_key);
    }
  }
}

And if you want to replace/overwrite either a default help tab title or content, just do what you’re doing in your code at the moment,

$current_screen->add_help_tab( 
  array(
    'id'        => 'overview-link', // by using the ID of a default tab you can replace title and/or content
    'title'     => __('Yay?'),
    'content'   => '<p>Yay!</p>'
  )
);

If you remove all default help tabs with the first code example (i.e. just call remove_help_tab() without the white list in_array() stuff), then it doesn’t matter which strings you use as ID’s for the new tabs you’re adding. The ID’s can be the default ones or something else.