Depending on the cause for the FAS, the doctors you see will vary. But since it is caused mainly due to a problem in the brain you will see a Neurologist and Neuropsychiatrist followed by a speech therapist.
2. Is the condition treatable?
Yes to a large extent it is treatable. By attending to the cause for the FAS and seeking some good counseling and speech therapy one can overcome this condition. But it does require a lot of patience as initially it may be an embarrassment to be suddenly speaking with a totally different accent.