Intended audience: parents of Autistic kids. Though obviously everyone needs Autistic friends.
So your child was just diagnosed with autism. Breathe. Breathe deeper. Relax. It'll all be ok. But you have some work to do.
The first thing you need to do isn't find therapists. It isn't commiserate with other parents. It isn't become an AAC expert (though all of these things have their place!). It's something not in the autism introduction packet: you need to connect on a human level with adults like your child. You need to go make some Autistic friends.
I don't mean a mentoring relationship, though those are extremely important and I am a big fan of mentoring (and mentoring your child & being friends with you are not mutually exclusive). I definitely don't mean "translate my child to me" (which is not a friend thing particularly). I mean find local Autistic adults with whom you have common interests and connect as equal human adult people.
There are a whole lot of reasons this is the best thing you can do for your child:
First, and possibly most importantly but mileage varies: your child is noticing things. If you go through a mourning phase, or a difficult adjustment phase, your child will notice and possibly blame himself. Your child may not have the vocabulary for it, but at some point he will figure out that he isn't the son you planned for and dreamed of, and he might blame himself for that. We figure it out when we're a disappointment, even if you do your best to hide that you're having a hard time. Many Autistic children get in our heads, accurately or not, that our parents only tolerate us because they're stuck with us.
Your child needs to see you choosing to be around people whose minds work like his. It's much harder to think your parents hate you and hate your brain when they seek out the company of people who think like you. Seeing the adults who are dearest to you--and like all children, Autistic youth default to loving their parents--seeing them find someone who reminds you of you? That's supremely important. Do not underestimate the effect this can have, just knowing that your parents would choose to be around you even if they weren't "stuck" with you.
Another reason: many disabled children never meet an adult with their disability. You might be surprised, and a bit saddened, at the conclusions we come to. Some folks come to the vague idea that we'll outgrow our disabilities (and when there's no sign of that, we're reminded that we're disappointing, because you can bet we're getting that message from someone in our lives). Or, I have friends who concluded that their disabilities were fatal. That's a recipe for severe anxiety, thinking that you're dying but you feel fine and no one has felt the need to talk to you about your inevitable demise. We need adults like us; this anxiety is completely unnecessary.
Your child also needs role models. She may not be able to fill your shoes, or Uncle Bob's or Auntie Bev's or her teacher's or those of any adult in her immediate sphere. But my shoes may fit, or those of another adult Autistic. All children need people in their lives who they can realistically emulate, & Autistic children are no different. I was pretty young when I knew the adult-woman things being modeled for me were just not going to happen ever--and alternatives were never presented. I was surrounded by folks who were similar to each other and not much at all like me. This is stressful. Making your own make is hard, and it's harder when everything you do is wrong (the premise of somewhere between many and most autism therapies, and a message also sent by peers, random strangers in the store, other adults, etc). Once again, anxiety. It's easier to believe you aren't Doing It Wrong when you know happy adults who took similar trails. Knowing options for the future? Seeing unconventional but fulfilling adulthoods? So important.
If you have culturally connected Autistic friends, your child also will have a head start on a connection to the community. As he grows older, he will have a life apart from your family. This is a good thing and an essential part of growing up. The Autistic community is his birthright. We as a general rule (can't speak for everyone) welcome friendly parents, but your child is one of us. It's wonderful but also overwhelming and scary to discover a place where you're "normal" when you've never been, especially all alone. Even good overwhelm is unpleasant when it gets too big. You can make this less of a shock by having Autistic friends. "I'm not alone" doesn't have to be an adulthood revelation; it can be a given. Your child deserves to grow up knowing that he isn't alone, that there's a whole community that will embrace him because he's one of ours. The gift of growing up with this knowledge? I cannot imagine it having anything but good effects.
Also, we're awesome. Autistic people are loyal and hilarious, among other things. We're good friends. We might provide insight to things about your kid that you never thought of, completely on accident. Your way of looking at the world may accidentally clarify things for us, too. But in my experience, Autistic people are the funniest people on earth, and the most dedicated to making sense and to fixing things that are not right (admittedly, my sample might be skewed, but I also have a very large sample size). That's how the people I hang out with roll. Making friends with us isn't just good for your child. We're good for you, too, and you can be good for us. A true friendship is a mutually beneficial relationship. We have a lot to offer each other.
So breathe, put down the pamphlets about all the different therapies, breathe again, and look in your networks for some Autistic connection. It'll make your life, your child's life, and some local Autistic's life, better.