Hi Sundday,
Welcome to the Heartland Owners Forum. There's lots of useful information here along with a great bunch of friendly and helpful people.
Although I'm not familiar with this unit, I would expect you have to remove the mounting screws that hold the player in the cabinet and slide the unit out to look at the rear, top and bottom. My guess is that the screw would be oriented to keep the tray from moving. So look for a screw that looks like it might be in line with the DVD tray.
Please let us know what you find.