I've installed some stoves myself and had others installed for me. Fireplace inserts are awesome if you get the right one, and you can get them EPA rated for 365 days burning (at least in the past; I haven't kept track of this because I am exempt where I live). However, the new regs probably added some cost to them and don't know what is being made that is compliant. Your fireplace should be grandfathered unless the county records were changed, which I doubt. As far as your chimney, depends on the install. The gas stove installers may have run pipe, which would need to be removed, and you would need to get the chimney inspected for damage. I would definitely do an insert if I had a fireplace. You can get them with pretty large glass too. I've used Goodrich Chimney Services, and I was completely satisfied with the work they did for me.