Is the movie in DVD form or a .mov on a DVD disc? If it's a DVD, convert the dvd to a quicktime (check out dvdxdv in the LAFCPUG store - or Mpegstreamclip on google)
Import the quicktime to FCP.
Add title. Render.
Export for DVDSP.
Burn new copies.
This will not be fast, but it's simple enough. And a lot cheaper than a post house.