[Samba] Migration to Samba 4

[Sonic]

Hello,

Currently have (and working for years) a Samba 3 PDC that also acts as
a file server and a print server. Would like to migrate the DC duties
only (at this time) to a Samba 4 AD on a new box without disturbing
user profiles (all SIDs, etc. remain the same), domain member joins
etc. Basically somewhat like an upgrade but on a new box with a new
name and then demoting the old PDC to a member server to seamlessly
continue its file and print serving duties.

I'm looking for a series of proper steps to accomplish this with as
little interruption and as much safety as possible. If anyone has done
this and can provide steps or a pointer in the proper direction it
would be greatly appreciated.

Thanks,

Chris