Add Node Tab - Best Practices

I posted the following to Module Development but now I realize that may not have been the correct location. Here is the message reposted:

Hello, Drupal community.

I am developing a Drupal integration with Gallery by which every content item (every node) has an associated gallery like so:
http://site.com/gallery/$node_type/$node_id

I don't need help creating or administering the galleries. I do not need help displaying images from related galleries on the item page or linking to the related gallery.

I would like, for administrators, editors, etc., a tab link next to View and Edit that goes to the administration page for that gallery. For the curious, this link will also create the gallery automatically if it does not already exist.

Now, I know that I can edit node_menu in node.module to add a new link. However, this technique is short-sighted: with any Drupal upgrade my addition will be overwritten and gone. How do I implement this properly?

Do I need to create a custom node module?

I appreciate the help. Thank you!