If I’m reading your question correctly, it sounds like you’re having difficulty adding the Quick Fields Agent snap-in to MMC. If that is indeed the problem, my guess is that you’re running a 64-bit machine. The Quick Fields Agent snap-in cannot be added in 64-bit mode. To launch MMC as an x86 program, just add a -32 switch to the command line when launching MMC.
So the full line would be: C:\Windows\System32\mmc.exe -32
Once it’s launched in 32-bit mode, you can easily add the Quick Fields Agent snap-in. If that’s not what you’re looking for, perhaps you can clarify where you’re running into trouble, and we’ll be happy to help!