The act of overfilling your trans would not cause the modulator to go bad.
Check the hose, check your fluid level.
If it is overfull, and the fluid looks nasty, but the trans works good, drain out as much as you can.
Take a good look in the pan, hopefuly you won't see much debris.
If that is the case, well just getting the nasty fluid out will go a long way to insuring that the trans will stay working good. Good luck!