[Plugin: WooCommerce] Help building a plugin to add functionality

I don’t know the first thing about building a plugin that will add functionality to an existing plugin. I’m hoping someone can share some knowledge or would like to chip in and help build that I’m looking for.

I’m a big fan of WOOCOMMERCE and WP E-Commerce but neither one does quite what I need. WooCommerce does pretty much everything that I want in an e-commerce except offering a better way of handling variances. I think that WooCommerce needs the functionality to have the ability to assign a +/- price change to a particular variance like WP E-Commerce does.

I’m hoping someone will read this and would like to help out. Thanks!