Installing an electrical box in an finished space is not a project for every homeowner, but if you are handy and willing to get your hands dirty it is not too difficult. Remember NEVER work with live circuits and if you have any doubts about what you are doing call an electrician! There are a ton of ways to get it wrong and end up killing someone or burning down a home.
The best way to check your circuits to assure they are off is with a non contact voltage detector. This will allow you to quickly check for voltage that could shock someone.
Below is a good article on getting it right, with lots of tipe about cutting in boxes, locating wires, installing outlets, choosing the right wire, arc-fault protection, tamper resistant outlets and more.
Read it here: www.buildconstructpros.com