My son as diagnosed at 3 so you are at a great advantage finding out now.
at 3 my son would say mamma and that was about it. He would grunt and make noises to ask for things or his brother did it. (we thought he was fine just big brother was talking for him too much) but after we noticed it was no improving once big bro went to kindergarten and he started having fits out of frustration at communications we enrolled him in speech therapy in our local district.
Most districts start speech at age 2 give or take. My son has been in it roughly 3 1/2 years now and has made amazing progress- he is now a well adjusted talking, interacting, communicating kindergartner. He still gets speech in school because he has some lasting speech issues due to not doing it for 3 years- as the docs explained it to me that most babies learn to verbalize before 1 year and he lost those 2 years of practice so hes getting it now.
The speech therapist said at his last meeting he has made it to roughly age 4-5 in his language/speech development so she thinks he will be caught up around the end of elementary school and he will be able to discontinue speech at that time.
The one tip that I wish someone would have told me is to URGE him speak. We were told that we made it worse because we would let him show us stuff in lieu of making him talk. That made him regress backwards towards infancy. So in hind sight I would say what we say now "Use your words, please explain what you want" sometimes he gets frusterated and doesn't know how to explain it and I just am patient and let him try a few ways until we figure it out and every time is less frusterating for him and his vocabulary is improving daily.
Good luck. Pm anytime if you want to talk... It can be frusterating and overwhelming but it can be overcome.