Hi mjsib2412,
Congratulations on your new Mallard and welcome to the Heartland Owners Forum.
Hopefully another Mallard owner will chime in to answer your TV mounting question. If not, you might call Heartland Customer Service at 877-262-8032 / 574-262-8030. Have your VIN # ready.
On the DVD connections, it sounds like your DVD player is either standalone or part of the TV, and the radio/surround sound system came with the trailer. We do have some entertainment center manuals in the manuals section of the forum.
Here's a link.
Often there's a bezel that dresses up the opening where the device is mounted. If there are no mounting screws on the bezel, it usually just pulls off, revealing the mounting screws for the device.