Have you had a chance to review the Woo Commerce plugin and themes? The unbelievably talented team over at Woo Themes never ceases to amaze us with new and improved functionality to our wordpress sites. You can download the free WooCommerce plugin and then upload to your exisitng theme or choose one of the Woo Themes specifically made for Woo Commerce. It installs in a flash and you are ready to add products, and set up shop immediately. There is beautiful integration with wordpress and you will find it easy to customize for the type of product or service you want to sell. You can add additional extensions for Paypal and other popular services.
Let us know if you need any assistance.