Ok, some things that might help with this project;
To access something over the internet you need to know the IP address of your connection from your IP. This is the IP that is on your router (I am assuming you have a cable or DSL internet connection, with a dynamic IP). You can try and keep track of it, or just register a domain name, and set up an automatic update service. www.dnsexit.com
offers a free service for this. Register your domain, and direct it to your IP address on dnsexit. They offer a free program that runs on your box to update the IP if it changes. If your domain name is mattycakes.com, you can do stuff like "ssh mattycakes.com", and connect to your machine from anywhere.
You have to direct the correct ports on your router to the particular computer that is running the server.
Try the slimserver software on your Linux box for streaming audio (Google Slimserver; you need the free software, not the device). Use vnc to see your desktop. Lots of other cool stuff is possible with a setup like this.