I wonder how I would know if the transmission is damaged? That is a much bigger deal than the torque converter.
It's pretty simple actually. "The fluid." This is how its been done since they came out with automatic transmissions. Doesn't matter is it has 2 speeds or 8. It is also possible for one part to fail and the rest to be just fine.
If the fluid color is very dark or black and has a burnt odor, you inspect the fluid and inside of the bottom pan for excessive metal particles or other debris. If large pieces of friction material or metal particles are found in the fluid or bottom pan, you have a problem. If there are no signs of transmission internal damage, then it should be fine.