You could write your own module with the intent of running it once. There is a Drupal hook_init() you can utilize to fire code when a module is on, and the page is loaded up. Within that function, you can query against all the nodes in the node table with db_query, iterate over each node and do a preg_replace on the link you want to change. After modifying the $node object, use node_save($node) at the end of the loop to save the node changes.
Alternatively, you can use a module like Link Checker, Path Redirect and/or Global Redirect to link old paths to new ones and look for busted links.