Divorce in a box? Is he serious? You have three kids together, this is not a case for "Divorce in a Box".
You have three kids' interests to look out for, do not fill out anything or sign anything without talking to your attorney. It's great if you can get H top agree to all your terms, but don't let him pull any fast ones on you. Lawyers are expensive but getting scr*wed in a bad divorce settlement is way MORE expensive.
Also _ I noticed you've been married ten years. If you were rounding up, do NOT let the divorce go through until it's been a full 10 years. It could affect your ability in the future to draw on Social Security in his name if you needed to (you have to have been married ten years). In fact, ten years is the magic number for a lot of things, so if you're just shy of that, figure out how to get to ten.