Trans Vacuum Modulator replace / fluid question...

[LandYaghtLover]

Going to replace the trans vacuum modulator since they are prone to failure and I have no control over my shift harshness. I assume failure of the part. If not, I have a spare.

Anyway, I read many, many threads on it. I only found one comment saying there is a "little" fluid loss. I want to be sure thats the case. So when replacing, how much fluid can one expect to come out? It may be relative to how full the trans is. But I need to know if I need to pick up some trans fluid before doing this.