Fireplace insert or a whole new fireplace
If your firebox and chimney are sound, an insert or a set of gas or electric logs in the opening you have usually costs less and keeps the brick you like, though logs are for looks more than heat. On an older brick chimney, I check its condition first, because loose chimney masonry can fall in an earthquake, and chimney repair may need to come first. A new build makes sense when there's no fireplace or the old one isn't worth saving.

