[Samba] Migrate samba3.5 classic domain to Windows2008R2

[Hoover, Tony]

I have a Samba 3.5.20 domain controller that provides logins and profiles
for our Windows XP computer labs on campus.  In earlier testing, we
encountered performance issues with Windows 7 logins.  Although that has now
been resolved, management is discourged from continuing to use Samba as a
domain controller.  I have now been tasked with migrating our classic
academic domain to Windows 2008R2 Active Directory.

Most of the documentation I have found on the subject is several years old
and involves creating a new domain and then migrating users/workstations
from the classic domain to the new AD.  I'd prefer to not create another
domain.

I have ~150 users & workstations, 30 domain groups, 5 local groups, and an
interdomain trust (to a 2003AD) to allow some administrative users access to
some academic resources.  

What is the simplest/cleanest method to accomplish the migration?  What
precautions do I need to take to make sure I can get back to the current
setup if migration experiments fail?

---
CONFIDENTIALITY WARNING:
Pseudo-legal disclaimers do not buy you or your employer any legal
recourse for leaked information.  E-mail messages should never contain
privileged or confidential information.  Always treat e-mail as
"public".