My best advice is to take good care of yourself and don't turn your life over to “cure” your son's autism. Make sure you have a support team of knowledgeable and caring professionals (occupational therapist, speech therapist, pediatrician) and loyal friends and family members who will listen to your concerns, offer comfort, and watch your child when you need a break (which you definitely will). Know that some people will profoundly disappoint you, but focus on those who come through for you and your family. If you experience what I did, you'll be flabbergasted at who fails you and who stands by you!
Also remember that, even though you may not know much about autism, you know your youngster better than anyone else and you more than anyone else wants what's best for him. Some professionals only see what's wrong with your child (his articulation needs work, his coordination is poor, his eye contact is bad) while you see the big picture: his kind heart, his loving touches, his compassion with his little brother. Don't let their negativity get you down because they're just doing their jobs. You'll eventually develop a tough skin, but don't forget to release your emotions in constructive ways. Don't keep your anger and hurt bottled up inside of you. Writing in a journal, talking to friends, and seeing a counselor are all things I did to help me cope.
Lastly, I'd say that exercise was essential to helping me get through my son's diagnosis and every day since then. I was prone to depression before that time, and the autism made it worse. Taking long walks, going on hikes, running on the treadmill, and going swimming helped me keep my spirits up and not get overwhelmed with negative thoughts. Exercise helped me live in the moment and take one day at a time rather than worrying about whether my son would attend public school, graduate from high school, go to college, or get a job.
I wish you the best as you and your son begin this next phase. Take good care of yourself and reach out for help, knowing there will be times when a person reaches back and other times when they won't. But just keep reaching!