Hi all ,
Engaging a contractor is possible if you have very flexible timing to be on site most of the time. It is hard for contractors to come out with 3D drawings as we know that most of them are usually uncles who are very experienced but not tech savvy.
An ID's job is to ensure that all works are done the way you want your house to be, to save you time and hassle by coordinating the different contractors to do up your house.