I need your help! I have two older steel heatilator fireplace inserts that have rusted out and cannot be safely used. I have two quotes wanting to charge me $20,000 to remove and build new inserts out of firebrick. Can’t afford this. Saw on YouTube where they cut the old firebox out, but give little details. Current fire boxes and surrounded by bricks. A- I want to keep these wood burning, is there a smaller insert I can install and avoid cutting out old fireboxes? B- if no, can someone give me details on how to cut out old firebox’s, tools, supplies, etc. . I attached a photo the type of firebox I am discussing. I can send more photos or dimensions if needed. Thanks for any feedback!