Inherited a theme I didn't create and trying to add nested comments

I inherited a website and have been trying to add nested comments to the custom theme. I tried following a tutorial I found online, but it broke the site when I tried them out. I’m copying my comments.pp code here in case anyone can point me in the direction of a good solution.

<?php // Do not delete these lines

	if ('comments.php' == basename($_SERVER['SCRIPT_FILENAME']))
		die ('Please do not load this page directly. Thanks!');

	if (!empty($post->post_password)) { // if there's a password
		if ($_COOKIE['wp-postpass_' . COOKIEHASH] != $post->post_password) {  // and it doesn't match the cookie
			?>

			<p class="nocomments">This post is password protected. Enter the password to view comments.<p>

			<?php
			return;
		}
	}

	/* This variable is for alternating comment background */
	$oddcomment = 'alt';
?>

<!-- You can start editing here. -->

<div id="commentblock">
<?php if ($comments) : ?>
	<p id="comments"><?php comments_number('No Responses', 'One Response', '% Responses' );?> to “<?php the_title(); ?>”</p>
	<ul class="commentlist">

	<?php foreach ($comments as $comment) : ?>
		<li class="<?php echo $oddcomment; ?>" id="comment-<?php comment_ID() ?>">
			<?php if(function_exists('get_avatar')) { echo get_avatar($comment, '50'); } ?>
					<span class="auth-name"><?php comment_author_link() ?></span><br />
					<span class="auth-time"><?php if ($comment->comment_approved == '0') : ?></span>
					<span class="awaiting"><em>Your comment is awaiting moderation.</em></span><br />
			<?php endif; ?>
			<?php comment_date('F jS, Y') ?> @ <?php comment_time() ?> <?php edit_comment_link('edit','',''); ?>

			<div class="commenttext">
					<?php comment_text() ?>
			</div>

		</li>

	<?php /* Changes every other comment to a different class */
		if ('alt' == $oddcomment) $oddcomment = '';
		else $oddcomment = 'alt';
	?>

	<?php endforeach; /* end for each comment */ ?>

	</ol>

  <?php else : // this is displayed if there are no comments so far ?>

 	<?php if ('open' == $post->comment_status) : ?>
 		<!-- If comments are open, but there are no comments. -->

  <?php else : // comments are closed ?>

		<!-- If comments are closed. -->
 		<p class="nocomments">Comments are closed.</p></div>

	<?php endif; ?>
 <?php endif; ?>

<?php if ('open' == $post->comment_status) : ?>

<p id="respond">Leave a Reply</p>

<?php if ( get_option('comment_registration') && !$user_ID ) : ?>

<p>You must be <a href="../stauffer/<?php echo get_option('siteurl'); ?>/wp-login.php?redirect_to=<?php the_permalink(); ?>">logged in</a> to post a comment.</p>

<?php else : ?>

<form action="<?php echo get_option('siteurl'); ?>/wp-comments-post.php" method="post" id="commentform">
<?php if ( $user_ID ) : ?>
<p class="betterformat">Logged in as <a href="<?php echo get_option('siteurl'); ?>/wp-admin/profile.php"><?php echo $user_identity; ?></a>. <a href="<?php echo get_option('siteurl'); ?>/wp-login.php?action=logout" title="Log out of this account">Logout &raquo;</a></p>
<?php else : ?>
<p class="betterformat"><label for="author">Name <?php if ($req) echo "(required)"; ?></label><br />
<input type="text" name="author" id="author" value="<?php echo $comment_author; ?>" size="48" tabindex="1" /></p>
<p class="betterformat"><label for="email">Email Address<?php if ($req) echo "(required)"; ?></label><br />
<input type="text" name="email" id="email" value="<?php echo $comment_author_email; ?>" size="48" tabindex="2" /></p>
<p class="betterformat"><label for="url">Website</label><br />
<input type="text" name="url" id="url" value="<?php echo $comment_author_url; ?>" size="48" tabindex="3" /></p>

<?php endif; ?>

<!--<p><small><strong>XHTML:</strong> You can use these tags: <?php echo allowed_tags(); ?></small></p>-->

<p class="betterformat"><label for="url">Comments</label><br />
<textarea name="comment" id="comment" cols="47" rows="10" tabindex="4"></textarea></p>
<p><input name="submit" type="submit" id="submit" tabindex="5" value="Submit Comment" />
<input type="hidden" name="comment_post_ID" value="<?php echo $id; ?>" /></p>

<?php do_action('comment_form', $post->ID); ?>

</form>
</div>

<?php endif; // If registration required and not logged in ?>
<?php endif; // if you delete this the sky will fall on your head ?>