Should be relatively simple. There is a bracket on the back of the tv that latches to the wall mount. Unplug all the connections, release the latches and remove tv from the wall mount. Unbolt the mount from the old tv and attach to the new tv, hold up near the wall mount ( you'll probably need a helper for this), plug in the cables and latch back on the wall. This is an over simplification, mount for back of the new tv may use different size bolts, cables may not be located the same, etc, but that's basically how it's done.
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