To get your plans approved by the building department, you'll need them signed off by an engineer (that's true in my city, and I'm sure in all other cities). Why don't you check with your bldg dept first, then get estimates from two engineers.
Please keep us posted.
In my town it is based on cost If project is over $10K then you need architect to draw up the plans or at least be approved by. I wanted to go to him with some knowledge of what to expect but I guess I will get the info from the architect.