The first thing I would do is get a book on fireplaces and read all you can. Depending on the weight and the material below the concrete, it should support a fireplace, if your not going all the way to the roof. If you are, you will have to build a foundation to support it. If the wall is block, you should be able to clean the surface with either block cleaner or sandblast any paint and debris off it. Then the morter will stick right to the block. The inside of the firebox needs to be made out of firebrick. This is kiln fired brick resistant to heat. As to if you go to the ceiling, it depends on the look you want to create.