You can preserve your oral heirloom by creating either an audio or visual recording of it. Both methods have their advantages, but only a visual recording captures facial expressions, clothing styles and other memorable details. Of course, all these visual cues can serve as an unwelcome distraction if you'd like the telling of the tale to be your heirloom's sole focus.
Either way, you'll want to go digital. Analog recordings (those using a "tape" of some kind) are prone to fluctuations and compromised sound quality. They're also more difficult to concisely archive and will have to be converted to digital at some point.
A digital recording represents sound in digital form. You can easily back up digital files on your computer's hard drive. Still, it's a good idea to preserve your oral history interviews in multiple forms. Transcribe the interview, print it to paper and make copies of the recording. And, by all means, don't store them all in the same place.