More info / cost to replace? Coal burning furnace converted to gas

Hi and thanks for any help in advance.

We just bought our first house (built in 1865) and have this in the basement. I understand it’s an old coal burning furnace that’s been converted to natural gas. Really just looking for more information about it - pros/cons, things to know, average cost to replace, urgency to replace, etc.

It heats the house fine but we can’t get it to distribute heat the basement itself. Based in the northeastern US