Sorry dude. It sucks.
1. You probably will lose some friends in the process. They will take sides whether you want them to or not, so if you have friends that are important to you, you need to stay close to them now and don't let someone else control the narrative. Hopefully she's cooler than that, but you never know.
2. Stay plugged in with your son. Don't let her do the doctor appointments, teacher conferences, etc. without you. It's easy to delegate this out if you're busy, but don't.
3. Agree never to badmouth each other with him. Draw a firm line with significant others.
4. Find a good attorney and be straight with each other on that. There are hard decisions to be made about who will pay for what, and you need help to document that.
5. Don't air your grievances, if any, in public, and def not here.
Good luck - you'll come out of it good, but the first few months will suck. Stay positive about the fact that you're choosing a direction for your life and not letting BIG MARRIAGE force you to stay somewhere that neither of you is happy.