TYou could name that "QuarkzZork" and you could still use it for a pain sound. Its where you put it in the hydralisk's playertype script that matters.
PainSound = HydraPainSound;
This is where is assigns that sound to the pain noise in the script.
Also, as for footstep sounds and such, I don't think there is a sound for walking. But if you overwrote the sound for spawning, I don't see why it wouldn't work.