Hi Liz:
Welcome to discussions!
This is a relatively easy procedure-it's just more difficult to explain than do..;)
First-let me ask you a few things:
Are you using audio that was imported on the original video (recorded on the Dv tape)? If it is, you will need to extract the audio.
Are you importing audio from another source-like iTunes?
You will need to know the length of the video you are deleting and make sure the photos are the exact length if you are wanting exact replacement and audio sync.
In other words, if you already have the audio where you want it and just want to replace a small clip of video with the photo, you will have to replace the deleted video with the same length photo...and remember-transitions will affect the lengths as well.
Know you're saying "...what?" about now. Post again if I have lost you .
Sue