Personally i'd say it's best you contact McAfee support so they can help walk you through this rather than trying to explain in laymans terms in just text.
If needed they can even make a remote connection to your servers to assist directly.
I have resolved this myself.
I exported the 1024 key, dont remember entirely how.
Addet the servers under the registered server, end imported the sitelist.
The agent migration worked.
And it didn´t have the be completely laymans text :-)
Im not entire novice, i have installed around 10 or so at customers