Here's the way I usually do it. Look for this code in product.tpl:
Code:
{include file="product_thumbnail.tpl" productid=$product.productid image_x=$product.image_x image_y=$product.image_y product=$product.product tmbn_url=$product.tmbn_url id="product_thumbnail"}
replace it with this:
Code:
{include file="modules/Detailed_Product_Images/product_images.tpl" }
Then just edit the detailed product image template as required to get it to show up the way you want it.