Can somebody explain to me how I could possibly repair my playstation

Could somebody please tell me how I can repair my PS2. It is the "fat" model. Not the slim line version. Machine starts up fine, but fails to read discs properly, for example: I will open a game on it and it will play the game for 5-10 minutes where it will then suffer a picture break up or freeze causing the entire game to come an unhappy halt. Also the disc tray will only open when the device is in the horizontal position and not in its normal vertical standing position. How do I go about solving these issues? Any help or advice on these provlems would be greatly appreciated. Thank you in advance.