If you have .avi files on your computer, yes that will be sufficient. Part of the problem is converting the video from analog video tape to digital .avi files, but that seems to be done for you.
You then import the .avi files into an editing program. The one I currently use is Adobe Premiere. It allows you to lay down the audio track and then place video above it, adjusting the length as you want. The current version of Premiere also will do the encoding for you into a Real Video file (Or Windows Media Player or Quicktime if you want).
There are a number of other Video Editors out there, but I"m not too familiar with them. I would check with
www.ulead.com and also
www.sonicfoundry.com. I think Ulead has a couple different versions.
If you buy an editor that doesn't have a built in RealVideo encoder, you will have to purchase that from
www.real.com as well.
Any questions are welcome!