Sophie depending on what you meant when you said you deleted the original audio this ashould be an easy fix….
first make a DUPLICATE sequence!!!!!!!
the original audio should still be on your drive, the audio is embedded in the same quicktime that your video is. Simply place the playback head at the head of a clip press “x” to mark the clip then “f” to open the match frame in the viewer. now, you should see both the video and audio tracks…simply link up the audio and unlink the video and hit f11…you should replace the tracked audio with the original from tape……
this all depends on the fact your audio is in the same file as the video…if not…. please provide a little more info..and we will see what we can do for you.. 🙂