Getting url from DB for redirect

My goal is to retrieve an url from a link field that belongs to the node(nid) inside an url. With that info I will be able to redirect to that url through this script.

The situation
From a product page I have an url "sitename.com/visit/?id=nid". This is configured inside the node--[content-type].tpl.php
The root folder "visit" contains a php redirect script named "index.php"

The script contains the following code which should get the nid from the url and use it to collect a node url inside a link field.

$id = $_GET["id"];
if (isset($id))
{
$link = mysql_connect('localhost', 'db_user', 'passwoord')
or die("MySQL is broke: " . mysql_error());
mysql_select_db('db_name');
$query = db_query("SELECT node.nid AS nid, 'node' AS field_data_field_deeplink_node_entity_type
FROM 
{node} node
WHERE (( (node.nid = '$id' ) ))");

$result = mysql_query($query) or die("Error while processing query");
$line = mysql_fetch_array($result, MYSQL_ASSOC);
$url = $line['node'];
header('HTTP/1.1 301 Moved Permanently');
header('Location: '.$url);
exit;
}
else
{
header('HTTP/1.1 301 Moved Permanently');
header('Location: http://www.sitename.com');
}

I used views to get the query but I'm stuck. I get confused with the changes of the update to D7 and the introduction with entities. And since the folder and script is in fact outside of the drupal structure I'm not sure if I'm approaching this the right way.

Cheers,

David