Need Help! How do you make a node/content-type a product in the e-commerce module?

I am trying to allow users to "buy" acidfree albums of photos for download via Pando. I've cloned the e-commerce file.module to create pandopkg.module and modified it so that it doesn't demand or verify a filepath -- instead, I plan to give it a URL at checkout time.

What I've done so far is to implement the following function in acidfree.module (borrowed from ec.media)

function acidfree_ec_pandopkg_nodetypes() {
  return array('album' => array('realm' => 'pandoPkg.module'));
}

I can then edit a previously created acidfree album to make it an ecommmerce pandopkg product. This seems to create a product out of the acidfree album, and in fact, I can manually construct a link to add this album to the shopping cart. However, I'm unable to get the "add to cart" link to show up when displaying the album. If I edit acidfree image to be a pandopkg product, then an "add to cart" link is properly displayed alongside the image. What's the hook that adds this link?

How do modify acidfree.module so that 1) I can display the "add to cart" link" and 2) change the way the album is viewed when I click on it from the shopping cart or products page?

Alternatively, the e-commerce file module has the following hooks:

/**
 * Node-managed file functions
 *
 * The following hooks allow third-party modules which contain files to treat
 * their files as products.  This module allows downloads only when the
 * products have been purchased.
 *
 * See also the ec_media module (ecommerce/contrib/ec_media).
 */

/**
 * Determine which node types are eligible to be treated as products.
 *
 * Invokes hook_ec_file_nodetypes.  Third-party modules must implement that
 * hook to be treated as products.
 */
function _ec_file_get_managed_types() {
  static $cache;
  if (!$cache) {
    $cache = module_invoke_all('ec_file_nodetypes');
  }
  return $cache;
}

/**
 * Determine whether a node is an instance of a node-managed product.
 */
function _ec_file_is_managed($node) {
  // sometimes node passed in is not really a valid node
  if (!$node->type && $node->nid)
    $node = node_load($node->nid);

  return in_array($node->type, array_keys(_ec_file_get_managed_types()));
}

How do you utilize these features?