How Can I Add An MP3 File Preview Feature to my MarketPress plugin?

I recently purchased the plugin MarketPress for a WordPress website I am working on. Due to the large number of downloads, and its high rating of 4.5 stars, this looks promising. I have tried some of the free e-commerce plugins and did not think they met my expectations. As I am a website developer myself, I would like to know more about e-commerce in WordPress. I have experience with ZenCart and Volusion, as well as static e-commerce websites using PayPal buttons, so I am not a complete noob.

The Question: I want to sell music in my website. The feature for downloading non-tangible goods, in this case MP3 files is present and understood. On the other hand, my client has requested that potential customers be able to listen to a 20 second preview of each of the MP3 files which will be sold. It might also be nice to be able to present a free sample of each of the CD albums which will be sold as well.

Instructions on how to add this capability to MarketPress by the development team would be fantastic, and much appreciated.

Jason Damisch