Domain Controller problem

[JH24]

I currently have the following

Server A
NT4 SP(6)
Exchange 5.5 (SP4)
PDC in Domain

Server B
W2K (SP4)
Exchange 5.5 (SP4)
Standalone Server in the Domain

Server A is a very old server that has had all the exchange data on it and i am currently swapping it over.

This is the current situation.
Server B now has all the mailbox stores on it, however Server A is still the DC and contains all the user logon names.......

How can i get this off this Server without upgrading it to W2K as it wont be able to handle it.
I am thinking that i have to put another server and do the following.

1) make it a NT4 BDC in the Exchange domain
2) promote this server to a PDC while it demotes the old exchange server)
3) then upgrade the new PDC to W2K, then promote Server B as well.

Does this sound like the way it should be carried out or am i making it overly complicated?

Thanks
J