Gas and wood pellet fire boxes retrofitted

Moving back to an old house.

The home to be has what was advertised as a decorative fireplace with a very pretty mantel, tiling, and ornate cover.

When they said decorative they meant it. Plaster wall behind it. It is an outside wall.

Thoughts about having a gas or wood pellet fire box retrofitted into the wall?

While the fire box is important, a proper chimney that is up to code is the most important.

I understood that these retrofitted boxes can be vented directly outside without a chimney.

Yes, I believe that you can get some boxes that are only the gas log type (not wood burning) that you can vent through the wall with proper insulation.