NT4.0 SERVER TO WINDOWS 2000 SERVER

I need to miggrate Winnt4.0 servers onto Windows 2000 servers. Now how do I do this?
I need to retain as much data as possible as well as do the migration over the weekend (2days).
NOTE:- The current WinNT4.0 is running on Old PII & PIII & the new machines are Proliant ML370T.
* Pliz do consider RAID options for me – I consider RAID 5.
* Security – Firewall or NAT
* One server will be running EXCHANGE5.5
* The other server will be hosting a SQL database, DNS, DHCP

All the best.