How to repair Toshiba SDP74SWB portable dvd player?

My Toshiba Portable DVD Player is not loading any disc's tries to load for a long time then says invalid disc, but this happens with all disc's. so I took a look at the lens and noticed that there was a loose bit which should be attached to the lens so I want to replace this part but how do I open the case without breaking the case as there are 3 screws on the back and 2 on the top of the bottom half, but the case still wont come apart as there's appears to be another screw at the back end which i cant get to to open the case