How to separate part of a Windows 2008 R2 domain and then add it to another forest?

One of our clients just sold one division of their company. They run two locations with basically a domain controller, terminal server, and file server at each location. They need to do two things:
1) Separate out one location so it is an independent domain.
2) Integrate that new domain into the existing framework we are moving into. I believe that this is a network running a 2008 R2 level domain.

So basically, I see two ways of doing this. Please let me know if I am on the right track, post any good links, and answer anything directly and simply if you can. I am not looking so much as the detailed explanation of how to do this, but more an overview of strategy to let us know the best way to proceed. Detailed questions would be introduced as further questions.

First way:
Separate out one location as its own domain and then join that to the existing forest.
1)_ Is this possible?
2) Is it a good idea?
3) Would this work if the new domain is 2012?
4) Any serious potential pitfalls?

Second way:
Remove the servers completely from the domain and then join them to the existing domain of the new owners.
1) I know this is possible, but is this a good idea? Better or worse than the first idea?
2) Will this work with Windows server 2012?
3) Any serious pitfalls?

Thanks!