How can I fix my Peagout 306 C.D player?

I have a Peagout 306 with a c.d player that was already fitted when I bought it. Recently my electrics went and when they came back on the stereo said i needed to enter a code. I wanted to buy the code on the net so tried to remove the stereo to get the serial number. I called Halfords to ask how much the tool was to remove it and the guy said you can get it out with a coat hanger, so I tried this but it didnt work so I bought the correct tool to remove it. But when I put it back the display had gone totally blank and it wont appear to switch on. I have never tried to enter a code so I dont see how it could have locked.
Any ideas please?