Best PHP code to display all images on node view, linked with Colorbox

I am creating a portfolio, and have a theme file [ node-project_design.tpl.php ] that overrides the presentation of the node. I would like to take images from one image field (that allows unlimited imgs) and
1) Display the first image larger on the page
2) Display the rest smaller next to the larger image
3) Link them all together so if a user clicks on any of them, they will open in Colorbox with forward and back buttons to other images in the array.

I used lightbox in the past, but would like to use Colorbox.

This is my code before:

		<!-- begin div.mainimage -->
		<div id="mainimage" class="field-field-image"><div class="imagecache-P_main_page_335w"><?php print $node->field_image_teaser[0]['view'] ?></div></div>
		<!-- end div.thumbs -->

		<!-- begin div.thumbs -->
		<div id="thumbs">					
		<?php foreach ((array)$field_image_teaser as $item) { ?>
		<?php print theme_imagefield_image_imagecache_thickbox('P_main_page_100w', 'Thickbox: thumb', $item['filepath']); ?>
		<?php }	?>
		</div>
		<!-- end div.thumbs -->

Not being a developer, I'm pretty much shooting in the dark with the php. Any help would be much appreciated.

Also, if someone has a better suggestion on how to deliver images like this more simply, please do share.