We have inquired with the original installer , Architectural Fireplaces , they told us entire unit has to be removed and rebuilt . Not estimate given .
Has to conform to Londonderry building codes upon completion.
We recently used NH Gas Fireplace Service, LLC (603-540-9858) (https://www.nhgasfireplace.com), we were very satisfied with his work. His name is Alan Coco. Feel free to call me if you have any questions.