My Portland DVD player won't open or close - help me fix it?

The slider in which you put the DVD will not open or close with the remote or the button on the machine. The cover over the opening is easily lifted with no resistance, but I don't understand the workings and don't know what to do next. Is there a trick to open this manually. Also, does anyone knows of a good "IDIOT" book for DVD player/recorder servicing? My deck is a Portland model # PVD 1000