Personally I would just have a play. You are looking for an earth (hopefuly black but who knows) a constant live and a live which only appears with the ignition on. Get a multimeter and get testing. The two lives will go to the red and the yellow on the back of a standard stereo, the earth to the black. If it loses its presets when you turn the car off, swap the red and yellow over.
The speaker wires tend to be different on all cars but are usualy obvious pairs eg a purple one and a purple with a black stripe. Find 4 pairs and experiment with balance and fader till you work out which speaker is which!
Dont blame me if you cook it but thats what I would do!
Cheers,
Mike