MarketPress single product and add to cart functions

Hi guys,

I'm looking through the MarketPress plugin for some code that will:

a) add a product to the shopping cart (as in add_product(product_id);
b) display a single product listing with title, description, image, variation, price, and an "add to cart" button

They seem like pretty essential e-commerce functions... do these functions exist anywhere? Can you offer some help getting started creating them myself?