I'm just wondering if it's possible to change the zombies' moans in BO1. I've managed to extract and listen to them from common_zombie.ff by using Tom Crowley's Black Ops Sound Converter Tool, but I see no way to repack my changes to the files. Is this possible, and if so, how would I manage to do it?

you can find zombies' sounds (moans) in raw\sound\vox\zmb\standard
in there you will find attack,death,sprint,etc am not sure but i think if you replace them with your sounds it will work am not sure i didn't try it
and also you have to convert your sounds with BassDrop so they work in game