Jimbo74...Mounting a tv bracket above a fireplace is actually pretty simple.  You want to get masonry ancors for it from Lowes or Home Depot.  I use 2.5 to 3 inch bolts.  It is good that you have a mantle to help the heat from going to the tv and harming it.  I have mounted plenty of t.v.'s above fireplaces, and that is the way to go.  I once mounted a 72 inch flatscreen, and that thing must have weighed a ton, but we got it up there.