How to link airport extreme wirelessly

So I'm about to buy an apple tv and my ultimate goal is to not have to use my MBP when watching movies (via my external hard drive). I found that someone had purchased an airport extreme and plugged their external directly into the airport extreme and it streamed flawlessly. I live in a huge fraternity house and our wireless networks are all in the basement (I live on the 3rd floor). is there a way that I can link an airport extreme to our existing network wirelessly so that I can stream directly from my external via an airport extreme? I'd like to keep the airport in my room and not in our dingy basement.

You still have to have the content of the external drive, regardless of how it accesses the network, in an iTunes Library somewhere. I assume this would still be your MBP. Just want to make sure you understand that your MBP will still be involved in this process.

Yes, you gan buy an AP and set it up to join your existing network very simply.

If you have a jailbroken AppleTV you can connect to and stream from a network attached hard disk.