Is there an API to Import /Update Items Automatically?

I’ve got a client that has a custom E-Commerce system built for their business. The Shopping Cart part of it is way outdated. We want to gut that part and replace it with CS-Cart yet preserve their Catalog Presentation scripts which rely on custom database tables for item, model, brand, etc information. This can be achieved by:

  1. Setup a conduit that creates and updates items in the CS-Cart DB using data from the legacy database

  2. Change code in CS-Cart that links to individual product screen to link to legacy script for presentation of product

  3. Re-skin to use legacy catalog presentation, removing links to all CS-Cart catalog functionality

    This results in having a custom catalog presentation system but then use CS-Cart for Shopping Cart, Order and Customer management.

    I’m trying to think of the easiest way to setup the product conduit. If there is a functional call or API for inserting or modifying a product, that I can use or am I in unchartered waters?