A Dolby Surround signal is actually just stereo. It contains only two channels of information.
Dolby Surround is actually a process performed on a stereo signal to produce a surround effect. Movies with Dolby Surround logos have simply got stereo soundtracks where the producers, with an understanding of how the surround process works, carefully mix the stereo signal in such a way as to produce predictable effects from this process.
All you need from your LD player to your amp is a regular, analog stereo cable pair. The amp does the rest, provided you have set it up to do so for this source. Use Dolby ProLogic or ProLogic 2.
If the soundtrack is not specially mixed in the way described, but it is stereo, then there will still be some rear and centre channel presence, but the rears will be much more subtle.
If the soundtrack is mono, expect your amp to route pretty much everything to your centre speaker.