^ you could use something from this upselling mod, it displays the thumbnails etc and if options are required then "add to cart" goes to the product details page instead.
http://forum.x-cart.com/viewtopic.php?t=6005&highlight=upselling+mod
I managed to integrate the checkout addon into the main template and I also figured out a bit more about smarty too, thanks much
Good luck with finishing the mod!