Fastest Way to Integrate with Existing Site

I want to use all the CS-Cart features EXCEPT anything to do with presenting products. We are going to write a 'conduit' program that will sync our existing inventory info with the appropriate CS-Cart tables. We just want to use the shopping cart and user account features.

Our current site uses CSS combined with HTML template files to generate the header and footer, etc. What do you think is the easiest/quickest way to integrate the cart and account screens into our existing site.

It seems we have two basic routes we can take. We can copy and paste our own HTML into the existing Smarty Templates. Based on my existing experience modifying CS-Cart Skins I know this will be time consuming as our templates are much more basic since we designed them ourselves, maybe 6 files combine to build an entire page whereas CS-Cart it can be dozens of smarty files so we would have to chop up all our files. More importantly, any updates we make to our own templates for the product presentation screens, we would then have to double the work each time and find the right smarty files.

The other route it would see would be to remove all the header/footer/sidebar content from the smarty templates in CS-cart so that all would be left would be the content. We could then create some sort of 'wrapper' script that would essentially build the page and insert the CS-Cart output into the content section of the page. I suppose this would be similar to just including CS-Cart in an iframe with all the header/nav/footer stuff removed.

Again, we CANNOT use CS-Cart for anything that has to do with presenting products and navigating the product catalog. Our existing site is custom made from the ground up. It is tens of thousands of lines of code with dozens and dozens of business rules for this one business developed over 7 years. But the cart/user part is antiquated. No Gift Registry. No Google/Amazon Checkout. Crappy coupon/promotion management. Very loose PayPal integration etc. Why try to reinvent the wheel when we can hopefully just plug in what we want from CS-Cart and run a conduit program to keep the CS-Cart inventory tables in sync with out own?

Any suggestions on the easiest way to 'plug it in' from an interface standpoint are much appreciated.

Replace header/footer with your own using hooks.

Turn off left/right sidebox blocks

Then set up links/buttons/tabs within your layout to get to the Account, Cart and other functionality you want. You may have to replace some of the controllers so that things like finishing the checkout takes you to somewhere different than the completed order page if you wanted.

Not really clear what the problem is you are trying to solve. But it's software so there's always a way. It's just a function of how much you want to invest to get what you want.