Three is the time when autism, which Asberger's is merely one point on that spectrum, does begin to show itself. The child could also have something else going on or could just be a strong-willed child. ADD/ADHD is another possibility but three is really too young to diagnose that. What you can do is start googling autism, ADD/ADHD, but please bear in mind that everything you describe is age appropriate and he may be just more determined to make himself heard. Separation anxiety, biting, most kids go through these phases and without proper transitioning, not wanting to switch from one task to another is really just flat out normal.
There is a woman that offices out of our church with Presbyterian Children's Homes. These folks work with a wide array of families with about a gazillion different needs and she consequently knows probably more about potential resources for parents, particularly in Tarrant County, than most people working in the field. Drop me a note and I can hook you up with her.
I would agree that the pediatrician is one of the first things I would do, find out what she thinks and what kind of testing and evaluating she could do and go from there.