installing a plasma on top of a fireplace

• I need some help with the installation of my TV on top of the fireplace.  I have heard about HDMI switch, but dont exactly undertsand how it works and which one is the best one I should get.  I have a DVD player and the Direct tv- DVR/ Reciever to connect to the tv.  I dont want to have wires sticking out of my TV.  There is only one Power outlet and a cable outlet on top of the fireplace.

Please recommend what should I do to connect DVD and Reciever to the tv without displaying my wires.

( I dont want to cut through my dry wall- Plz let me know the alternative)

Thanx!