It took me forever to get this script set up exactly the way I wanted it - but, I finally did it.
If you have a Zen Cart store, and you want to accept only Google Checkout, (like me), all you have to do is this very simple "cheat":
In your shopping_cart.php file, modify the dimensions for the script's "built-in" checkout button (your_template/buttons/english/button_checkout.gif) to: 1px x 1px. I'm sure that it's also possible to simply make the dimensions 0px x 0px, I just haven't done it yet. To see how this worked in my store, you can see it here:
http://url7.org
Now - when a customer is ready to checkout - all they will see is the Google Checkout button. This is with Level 1 GC integration - but it works perfectly. Everything that is added to the cart will appear on Google's secure Checkout page with the total already there, (so this also eliminates the need for an SSL certificate on your end); and, since the Google Checkout button is the only button your customer will see when they are ready to checkout, there is no confusion, missed orders, or non-paid "completed" checkouts... as I'm sure there is sometimes confusion on the customer's part with the "two-button" checkout setup, (where you have the built-in checkout button, then the "-or-", and the Google Checkout button below that). I was almost at the point where I was simply going to send a payment request to every individual customer who "completed" a checkout without using the GC button (anyone who has tried to use only Google Checkout Level 1 with Zen Cart knows that a customer can actually "complete" an order without actually paying)... but now, that won't be necessary, because they can't "complete" an order without using the GC button itself.
(NOTE: I will be adding the "Powered By Zen Cart" link back to my store site before I begin the tedious work of promoting the store; probably a button or banner, instead of only the small text link. This is an excellent script that deserves a link on every site that uses it).
A word of advice: if you ever get frustrated trying to get this script to work for you.... KEEP TRYING ANYWAY. Dig down into the code... find where the things are that you want to change, one at a time... and most of all, keep a backup of everything as you work so you don't end up with a horrible looking mess. You CAN make Zen Cart work for you, as long as you don't give up.
Good luck to everyone who is working with this fantastic script. It will do pretty much whatever you want: but - if you want anything beyond the default "classic" look, you'll have to put some time and effort into it.
Besides posting this simple work-around, I also want to thank the Zen Cart community personally for the outstanding work and effort that has gone into this script. My wife and I have a son with brain cancer, (glioblastoma multiforme, you can visit our son's page at: http://www.caringbridge.org/visit/ryanotto ), and my successful installation and setup of this script will allow us to stay at home with him during this very difficult time. If someone can explain to me how I can add custom text and links into one of the sideboxes, I need to add text explaining that 10% of all this store's profits will go to the Pediatric Cancer Research Foundation, and also a button-link to http://www.pcrf-kids.com/ in case visitors want to make direct donations to PCRF, or simply find out more about pediatric cancer research.
Again, a sincere Thank You to the entire Zen Cart Community.



