How to convert joomla(ACL) from joomla 1.5 to joomla 2.5 version-Collection of common programming errors

I have a function in joomla 1.5

function saveuser($row){
    $db =& JFactory::getDBO();
    $instance = new JUser();
    jimport('joomla.application.component.helper');
    $config   = &JComponentHelper::getParams('com_users');
    if(!isset($row['usertype']))
    $row['usertype'] = $config->get( 'new_usertype', 'Registered' );

    $acl =& JFactory::getACL();
    if(!$row['gid'])
    $row['gid'] = $acl->get_group_id( '', $usertype);

    $instance->set( 'id'            , $row['id'] );
    $instance->set( 'name'          , $row['name'] );
    $instance->set( 'username'      , $row['username'] );
    $instance->set( 'password'      , $row['password'] );
    $instance->set( 'email'         , $row['email'] );
    $instance->set( 'gid'           , $row['gid']);
    $instance->set( 'usertype'      , $row['usertype'] );
    unset($instance->password_clear);
    unset($instance->guest);
    unset($instance->aid);
    $ret = $db->insertObject( '#__users', $instance, 'id' );
    if(!$ret){
        return false;
    }
    $acl->add_object( 'users', $row['username'], $row['id'], null, null, 'ARO' );
    $acl->add_group_object( $row['gid'], 'users', $row['id'], 'ARO' );
    return true;
}

But when run as joomla 2.5 is error is:

Fatal error: Call to undefined method JAccess::get_group_id() in ... on line ...
Fatal error: Call to undefined method JAccess::add_object() in ... on line ...
Fatal error: Call to undefined method JAccess::add_group_object() ... on line ...

How to fix this function to joomla 2.5, How to ideas ?