What is ahead of me?

Hello! I am new to this forum. I am getting ready to make a doctors appointment to see if I have ADD. I am feeling a little (ok alot) overwhelmed about all of this and wondered if anyone could give me insight in what takes place at these doctors appointments? I have read where some have had to take 6 hour tests and go through extensive background medical investigations. Can anyone who has already been through this give me some information? I am not sure if I should start off with my primary doctor or find a psychologist.

My doc just started asking me questions and was quick to diagnose, but I agree with him that I have a "pure" form of Inattentive ADD and no other conditions. If ADD (or any other condition I imagine) is left untreated it can lead/cause other conditions. It took me from 9 to just two weeks ago at 34 to finally tell someone that I think something is wrong with me and I'm glad I did. My doc is glad I came in so early in life.