You may want to make sure that DS is completely clean before you begin. Check for stuck Obituaries, TimeSync issues, etc... Its best to do these kind of upgrade with DS as healthy as it can be.
BTW... Have you ever run a DSMAINT "Prepare NDS for Hardware Upgrade" before? This will make a BACKUP.DS file in the SYS:SYSTEM directory. When you run this procedure, it literally will "suck" NDS off of the Server, create the BACKUP.DS file and close the DS Database. Once you have done this step, just go to the next DSMAINT selection... "Restore NDS after Hardware Upgrade". This will re-establish and open the NDS Database. Now you can copy the BACKUP.DS file from the SYS:SYSTEM Directory.
We use this procedure whenever we are about to do any major changes to any of our Servers. It makes recovering from problems a bit easier.
Good Luck!