We’ve replaced our wood burning stove with a gas stove, as well as adding an additional gas stove. We LOVE them. They are our only heat source in the house (1100 sq ft).
I did both installations myself, but you’ll likely need to get a permit for the gas line installation. The cost will depend on how far you need to run the gas line to tie in with your propane or natural gas lines. A plumber can give you a quote, but I would estimate $500-$1,000 for the gas line.
The stove itself will be in the $2000-$5000 neighborhood, depending on size, BTU, thermostats, fans, etc.
The chimney piping will also need to be replaced to some degree, which will add between $200-600 in materials (the chimney piping is obscenely expensive for what it is) plus labor costs (perhaps a couple hundred).
Hopefully that gives you a rough idea. I can give more details on any of the above if you’d like.