I am in the process of a similar setup but I am putting a direct vent fireplace in.
1 - the venting may be different. My old fireplace had larger vent tubing with three inside chambers. The new one is smaller with one inside chamber.
2 - the required clearance to combustibles may be different on not only the new stove but also the venting
3 - My direct vent fireplace required a sealant around the vent called Mil-pack and had to be sealed where it met the fireplace and where it exited the house.
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