Hi Stephen,
When you say old DFM server to new instance of OC5. Are they on different systems all together ?
Old DFM Server: SERVER1
New OC5 Instance: SERVER2
If your situation is above, take a dfm backup using "dfm backup create" from SERVER1 and restore it in SERVER2 using "dfm backup restore <backupFileNameTakenInServer1>
By doing this you dont have to do anything in the SMO dataset.
If your situation is on the same server then you just have to run your OC5 installer and upgrade, which is seamless.
Regards
adai