This is a picture of one of the forges in the guild I belong to. We have 8 in our school. We use a standard firepot from Centaur forge with inside dims. of 8x10 The cut out is roughly 10" wide, the length of the firepot. The height is also about 10".
An exhaust fan in the chimney will work but not necessary. When starting the fire put some newspaper into the draft box and light it preheating the chimney with an upward flow of hot air that will start the draft. While that burns, light your firepot and use low to med low airflow to bring the coal to temperature.
I understand about the coal smell. My wife can not stand the smell of the coal, so I'm always being told I stink. The hood and chimney won't help with that. You'll still stink.