$resource = $modx->getObject('modResource', array('id'=>$id));
$newObj = $modx->runProcessor('resource/duplicate', array(
'id'=>$id,
'duplicate_children'=>true,
'name'=>'New Obj '.$resource->get('pagetitle')));
This question has been answered by Bruno17. See the first response.
if ($response->isError()) {
$updateerror = true;
$errormsg = $response->getMessage();
}else{
$r = $response->getObject();
if (isset($r['id'] && $resource = $modx->getObject('modResource',$r['id']))){
//do something with $resource
}
}