Fireplaces, Heating Stoves, Flues and Chimneys - open a sealed up fireplace?

I have a brick fireplace that has been covered with sheetrock. I would like to remove the sheet rock at the fireplace opening and place an insert inside the opening. My question is do I have to remove all the sheet rock- or just punch a hole at the center and remove the sheet rock until I get to the end of the brick. If the fireplace looks bad can I buy a mantle and cover up the brick? When I bought the house FHA said the fireplace looked perfectly good on the outside.
thanks ......

Contact your local chimney specialist before beginning your project. Any repairs to the chimney is best done by a professional. A professional inspection will help you know what you are up against as far as repairs, relining, and your budget.

Keep in mind if your house is old the fireplace may be a Rumford design - very shallow firebox which would probably not allow for an insert.The few fireplaces I've uncovered behind plaster walls ended up being the Rumford type.