Keeping an old fireplace or adding an insert
If your fireplace is sound and you only light it a few nights a year for the look, it may just need chimney repair to keep it safe to use. If you want it to heat the room, I'd put in an insert, because an open wood fire is a very poor heater, with drafts pulling the room's warm air up the chimney. A gas, pellet or certified wood insert gives you more heat with less smoke.
What shapes the cost of fireplace installation
The biggest swing is whether we're reusing what's there or building new. A direct-vent unit is priced higher than an insert, since its price carries the labor and parts for a whole new vent setup. On an insert job, a chimney that needs a new liner adds to the number. New framing, the gas line run, the unit you choose and the surround material you pick, plain brick or stone, move it too.