get a wire hanger cut it into 2 u shape pices slot them into the holes on the frunt of radio where the 4 holes are put some presure on them and pull the radio from the tape deck just did this today...
On a Peugeot 806 car stereo there are two thin pieces of black plastic at each side, you need to gently prize them off, and that reveals 2 screws on each side you can then remove the stereo....
With difficulty it takes a professional mechanic with all the tools about 5 and a half hours, if you try and do it at home it will take longer. it would be very much worth buying the proper Haynes...