I'm responding to this as the child of multiple divorces, the friend of many who have divorced and the sister of the stepmother...
1. DO NOT share a lawyer. Find the best you can afford; you're going to need it.
2. Sit down and do a realistic budget for just you and your kids. Be sure to include day care costs as you return to work or school, insurance, home maintenance, children's activities, etc. You should expect him to pay alimony and child support until you're up running, particularly if you've been out of the work force to care for the family. That's a job, too. (Personally, I'd keep subbing as you work your way in to a teaching position.)
3. If your husband is as "done" as he says he is, he should move out. This should happen roughly five minutes after he has explained to his children why he's breaking their family apart. Hiding out in the basement and expecting you to carry on is the act of a coward.
4. Find yourself some counseling. You're going to need it.
I don't know how it is in Illinois, but in California and Nevada (where I lived/live), the courts favor the mother. Your husband may be a lot less "done" when realizes how much he'll be giving to you and the kids and how little he'll be able to keep for himself.
My sister, who is a veteran of many a day in California family court (as wife of the ex-husband), would advise you to document everything and to do your research (she likes to call it "due diligence").
I'm not advocating that you "soak" your husband for every penny or that you purposefully act in an obstructionist way. But, it is your job to make sure that you and your children do not suffer unnecessarily because your husband is "done." Revenge has no place in divorce proceedings.
Next, whatever feelings (good or ill) that you have for your husband must be handled away from your children. Whatever you do, DO NOT bad mouth, trash talk, or be disrespectful of your soon-to-be-ex in the presence of your children. Remember, he is still their father. I can't tell you how many times my mom did that and how poorly it reflected on her.
Last but not least, when a step-mom comes on the scene, don't freak out. You are NOT being replaced as mom. I've had two stepmoms and neither of them wanted to "be my mom." What they wanted was for me to develop a better relationship with my dad. With my first step-mom, that meant having us over every weekend to be part of her family (four kids and my dad). My mom went bananas thinking she was trying to "steal" us away from her. (This was after years of complaining that my dad never did anything with us!) With my second stepmom (I was an adult by this time), she also wanted my dad to improve his relationship with me (and my sister). My mom got upset that I spent more time talking on the phone with my stepmom than with her (in reality it was fairly equal). My sister tried being an involved stepmom--looking after my step-nieces grades, for example--and the mom went nuts. My sister was "interfering" with her "rights" as mom. Never mind that all three step-daughters were failing school and with my sister's intervention their grades improved, in one case to the point where one of the girls earned her way out of alternative education and back into regular high school. In all three examples, mom sounds like a psycho, huh? Don't be that kind of mom. Again, it will always reflect poorly on you.
I'm so sorry you have to go through this. Hang tough, sister. I know it's hard to believe this, but you can survive this and so will your kids. It won't be easy but you will.
Hugs...