Add New Product Type to Zen Cart

I would like to add a new product type to my Zen Cart web shop for individual machine embroidery designs. I have a table (spreadsheet layout) that is used by other vendors and I would like to remain compatible with it. I can supply this file with sample data (includes variable names and types). They use this table to import directly to their databases. I'm looking for someone who has had experience doing this. Specifically I'm looking for any necessary revisions to the required php files, revisions to any zen db tables, and the addition of new table(s).