Urgent help - quick fix? Broken site after installing Ad Manager addon

I was loading the files for the Ad Manager mod and then proceeded to test the checkout process and then the checkout confirmation page was broken. I removed all Ad Manager files, but it's still broken with this error:
Fatal error: Call to a member function process() on a non-object in .../includes/templates/apple_zen/templates/tpl_checkout_confirmation_default.php on line 180

Line 180 has always been the same and wasn't modified:

<?php
  if (MODULE_ORDER_TOTAL_INSTALLED) {
    [B]$order_totals = $order_total_modules->process();[/B]
?>

I'm not a programmer and was simply trying to install Ad Manager based on this post http://www.zen-cart.com/forum/showthread.php?t=113071&highlight=ad+manager. Can someone point me in the right direction based on the error message? :cry:

I have not used this module, so cannot help with specifics, but the general rule is this:-

If a module OVERWRITES existing files, you should make a BACKUP of those files before you install the module. The same "rule" applies if the module modifies the database - backup the dbase first.

To "un-do" the faults, you need to get your setup to the point where it was BEFORE you installed the module.

So...

1. Remove all ADDITIONAL files that the module loaded up.

2. Replace all files the module overwrote, with their originals from a set of the core files of the version of zc you are using.

3. (if necessary), RESTORE your database from the backup.

Thank you for the tips. I backed up everything before implementing the mod and tried to replace the necessary files, but I'll try again. Just wanted to make sure I wasn't missing something by encountering a common error message. I will check back with you soon.

Fixed the issue by replacing a couple of core files. The Ad Manager mod has a couple of instructions that broke my checkout page, so I reverted back and it seems to be working at the moment.