I've hung 2 TVs, a projector and have run/hidden tons of wiring throughout my house. It's not hard at all as long as you take your time.
o Make sure you're not drilling into any power lines, ducts, etc.
o Use a stud finder to find/mark the studs. Now check again and maybe a 3rd time
🙂
o Follow the directions that came with your mount. It should specify what size drill bit you should use, exactly where the holes will go, etc. It should come with a template to make it easy.
o Prior to hanging the TV on the wall, I usually test the mount by seeing if it can hold my weight (assuming it's rated to hole that much weight).
o Hanging the TV on the mount is easy. You attach a mounting plate to the back of your TV and then, literally, hang it on the mount and then secure it. This is quite a bit easier these days since TVs a lot lighter than when I first did it.
You have lots of options in regards to hiding the wires. I bought most of my wall plates and whatnot from monoprice.com. For my living room and home theater, I used keystone wall plates and jacks.
When it comes to power, you have 3 options:
1) Just have it hang down the wall or in a cable race-way type thing. In other words, not in wall. This is the easiest option but you'll see the wire/raceway.
2) Run an outlet to behind the TV. You can decide if you're up to this or if you'd want an electrician to do it.
3) Use something like a power bridge, like this company sells:
http://www.powerbridgesolution.com. These are basically in-wall power extensions that are legal to use. You have a normal outlet behind the TV, a male outlet on the bottom of the wall and a romex/electrical wire connecting the 2 in-wall. They are very easy to install as long as you're not afraid of cutting holes in your wall and can handle hooking up an electrical outlet. I've used these twice. Another advantage of these is that you don't need to worry about mounting a surge protector behind your TV. They sell versions that can handle not only power but the A/V cables as well.
Don't simply run the TV's power cord in the wall and don't run a normal extension cord in the wall. option 3) is a legal way to do that.
Hope that helps.