You should get all the url of the old site with Xenu's Link Sleuth, then create a PHP array of oldUrl => newUrl and put it in your redirect script.
So you have in the htaccess :
RewriteCond %{REQUEST_URI} ^/home/newscontent.asp
RewriteCond %{QUERY_STRING} id=([0-9]+)
RewriteRule ^(.*)$ redirect.php?id=%1 [L]
In the redirect.php file, you have :
$redirect = array("/home/newscontent.asp?id=1133" => "/name-of-the-article"); // 800 times (for all url)
if(isset($redirect[$_SERVER['REQUEST_URI']])) {
header("Status: 301 Moved Permanently", false, 301);
header("Location: http://www.mydomain.com/".$redirect[$_SERVER['REQUEST_URI']]);
exit();
}
// Send a 404 if you don't have a redirect