Go here. You will find all kinds of release forms that cover both books and movies. If you don't find what you think you need don't hesitate to join the forum and ask specifics. The chances are someone will know the answer, just remember that much like this forum not everyone knows as much as they might lead you to believe, so check any information out before you use it.
Don't write about a living person without a release if you can help it, and don't give them the right to have final say on what you have written.
It is not slander or libel if you can document and prove everything you have said, but it might be invasion of privacy. Also you are not supposed to hold someone up to ridicule (unless the person is a celebrity in which case they have few if any rights at all)
But don't despair. These are not insurmountable problems. If they were no such book as yours would be written.
Also because of your position you might very well have access to legal assistance from a group that would like situations such as you would be describing exposed completely and battled more effectively. I know there must be a group out there who would love to back you and have you laud them in your book for having done so.
And while we are discussing your unique position you might very well have a wonderful option here. Write a book proposal and ask for a grant. I have been told There are grants out there for from $50,000 to $300,000.
