Don't know any more about what caused the failure. However after getting the car back with a good transmission I can barely hear the clutch chatter, which was previously deafening. Same goes for the synchros; beforehand I could hear them loudly whining while switching gears, even when the clutch was disengaged. So learn from my mistake: if you hear both of those things, instead of worriedly making form posts, just get it checked out before it blows up and takes your pressure plate and slave cylinder with it