creating a trust

Hi all!

I am designing an Active directory network to replace the old active directory network.

I want to create a trust to migrate users, groups, etc from the source domain to the destination domain.

Have a couple of questions.

A) Only want to create a 1 way trust but can't remember which way round i need to do it!
Want to use ADMT to migrate from source to destination. I need to set up a conditional forwarder but not sure which domain i set this up in.

B) both domains have the same first part for the dns domain name (source)
(destination)

can i still set up the trust, bearing in mind the first part is the same.

hope you can help.

thanks all