Write down what is there now
Distinguish an open masonry fireplace from a factory-built fireplace with a manufacturer label. Photograph the front and save the model information if available. For a factory-built host, compatibility is an explicit question for both the appliance and the existing fireplace. A surround panel that hides the gap around an insert tells you nothing about the fit behind it.
Read an emissions listing for the correct product
EPA distinguishes wood-heating appliances such as wood-burning inserts from conventional open fireplaces in its emissions programs. Search for the proposed insert’s model in the EPA wood heater records when comparing a seller’s emissions claim. A manufacturer listing for the new insert does not verify the condition of the chimney in your house.
Compare the whole installation scope
Ask who evaluates the existing flue, which vent components the insert requires, what hearth clearances apply and how the system will be accessed for sweeping. Make the proposed appliance, venting, finish work and follow-up maintenance separate entries on the estimate. A price for the boxed appliance leaves those other decisions open.