It sounds like you have great resources lined up. Take a deep breath and just enjoy him while waiting for the results of the evals come back. If the OT diagnoses SPD, they will recommend a sensory diet--simple exercises or practices to do at home, and they may recommend you see the OT as well. How often depends on the diagnosis. I know some who see their OT twice a week, some once a week, some twice a month. The great thing is that they are evaluating him early. If he does have SPD, that increases his chances dramatically of functioning in the normal range in the future (see The Out of Sync Child by Kranowitz). It is normal for the doctor to recommend an evaluation by a developmental pediatrician, and that doesn't mean he has autism necessarily. I'm glad to hear you see a happy little boy. That is a blessing in itself!