Just brought this Disco and it has a rear subwoofer, but since the last owner added a Kenwood CD player the sound is a little 'tinny', how can I reconnect it?

Also I would like to replace the speakers in the doors (probably just the fronts to start, what fits? I saw alot with no covers on when I was looking to buy a Disco and it looks very naff!!!

You need to send a line out to the sub in the doors, assuming it is the model with an amp behind the subs. The cables if I remember are black and red these need to go the positive connection of the line out put.

There is always a chace that the speakers are nackered as I have seen loads like it. So take of the grill and gently and evenly press in the cone to see if there is still movement in the voice coil. If it is nackered then it will be solid.