For each Windows Autentication Login you need to create another login in the new DOMAIN.

You need to change the account that start the SQL Server services if that use a Domain account.

I change my DOMAIN a few month ago. Try to translate this post:

http://www.mcdbabrasil.com.br/modules.php?name=Forums&file=viewtopic&t=3595

I'm from Brazil. I have a basic English. I hope help you.