Reinstall Windows 2003 server while maintainig Active Directory

I have two servers.
S1 is Win2003. S2 is Win2003 R2.
S1 was the first server in the forest. I just added S2 and made it a domain controller.
I want to wipe S1 out and install Win2003 R2 on it also. I could probably just upgrade. However, I have been having some problems with this server and I would like to do a clean install.

I know that there is no longer a pdc and a bdc. However, I also know that the first server in the domain has the FSMO role. I plan to transfer the FSMO role to S2,
        install Win2003R2 on S1,
        re-join the domain with S1 and
        then transfer the FSMO role back to S1 (my stronger server)
       S2 is a DNS server
       S2 is running DHCP
           I split DHCP scope between S1 and S2
              DHCP is setup as follows
                  S1 = 192.168.1.1
                     DHCP scope is 192.168.1.100-150
                  S2 = 192.168.1.2
                     DHCP scope is 192.168.1.151-200
I have never done this process before and I am sure it is not as simple as I envision. What else should I be aware of?