Copy anything & everything financially that you can get your hands on - your tax returns dating back at least a couple of years, copies of car titles, insurance policies, house deeds, bank statements, etc. etc. If he has a retirement account, copy that. You will need (if you work), copies of your W-2's, etc. It is much easier on everyone if it can be amicable, especially with children. Wish I could say that mine was, but it wasn't. We ended up in mediation. States are different, too, about property division. There IS a light at the end of the tunnel, but it's a long tunnel, & I know at times I thought I'd never get through it. It may be something you want &/or need, but it's still a loss, so you'll grieve. With children involved, you will still have to have a relationship, & that can sometimes seem like it will last forever. Hang in there! Hopefully, you have a good support group around you - family & friends.
It may seem overwhelming, but just do one thing at a time - focus on one step at a time, & you'll make it! {{{{{HUGS!}}}}}