I'm renovating a large 1968 Heatilator fireplace that has two vents on both sides of the tumbled marble fireplace surround with old fans in the bottom vent that no longer works. There is also another fireplace in the basement that seems to be connected to the vents on this fireplace. Originally, there was a glass bifold door that needs to be replaced. We are looking to install a new glass door and need recommendation on what kind of door would make this fireplace most efficient? Is it best to install a door that has ceramic glass so the door can be kept closed while in use with a front vent? My research indicates a tempered glass door needs to be open when using the fireplace. Also, is it necessary to replace the vent fans? If so, any recommendations on where to purchase them? The opening is 42" wide x 27" high. See the photos. Any help would be greatly apprecaited!