Home theater design help

Recently I discovered that a wall I did not I think I could move is actually removeable and thus I can more than double my current home theater room into a much larger home theater/ media/ entertainment space. I engaged what dealers remain in my area but none seemed all that interesed or capable of managing design and construction changes especially since I have most of the equipment already. Anyone have any ideas on how to pursue this?  I roughly know what I want but also know there’s likely a lot I don’t know around design, sound tailoring, decorating, acoustics etc.   kind of at an impasse currently. Thanks!