Upgrading NT4 Domain to 2000

I just had a question, when I upgrade the NT4 PDC with 2000, are the user passwords going to stay the same? or are they going to have to create new ones once the upgrade is done? Also, what is a good resource for me to look online on different ways of upgrading an NT 4 Domain to Mixed mode active directory? I have other NT4 bdcs at remote sites systems that need to be in mixed mode for now.

Any help on this would be appreciated.