Car Stereo wiring

[renault!]

I have just put in a new stereo, but as I was putting it in the radio adapter touched some metal and sparked and then the stereo would not work. So I was told it had just fused so checked the fuse box but this was ok, and the stereo works in another car, So the wiring inside must be faulty somewhere (all other electrics are working) can these wires that attach to the stereo and radio adapter be replaced and is it easy to do and any ideas how much this will cost???

Please help because this is really frustrating, I miss my music!!!!!