Understanding the framework of the php

[zac]

Hi.. I have hacked up my coppermine into barely recognizable form thanks to all of the great help on these forums.  Having such a partial understanding of everything, I am having trouble knowing where to begin with certain problems.  The biggest hack installed  is madeinhawaiis Client Side Shopping Cart. 

http://forum.coppermine-gallery.net/index.php?topic=25182.0

When you click the shopping cart it opens up a new .php document that is wrote strictly for ordering prints called purchase.php.  I also have the vertical thumbs hack running. 

The problem is when the shopping cart is opened the thumbnails disappear and the option to resize the image by clicking it is dead.  Can someone tell me where to start to fix this? 

Is there something online that I have missed that gives a decent explanation of the structure with this.  If I call up this new php what happens to the hacked thumbnail that is in my theme? Any idea of what piece of script is being replaced?

If you have no idea what I am talking about I set up a test gallery here:

http://www.folkphotography.com/prints/

username: test
psswd:  test

I would post some code if I knew where to begin. 

Thanks so much to anyone who is willing to tutor me a bit with this and get me in the right direction.