I don't really think there is a proven way to tell if it was fixed. I don't think Ford documents this, at least if it was done by a dealership. I fixed mine, and it's pretty obvious b/c of the larger, alum. radiator that is clearly not stock looking. You'll just have to look and see for yourself.
The Ford cooling "fix" didn't always work according to some threads I've read on various forums.
Best is to use aftermarket parts (Steeda, flodyne, etc) radiator and install yourself.
The Ford fix would set you back about 1200 in parts + labor. I have seen some butchered installs of this.
As far as the cooling "problem" goes that is essentially what is needed.
The cooling issue is really the A/C condensor position in front of the radiator and that the cooling fins on it are so tightly spaced. The existing radiator is aluminum but the cooling capability is reduced by the A/C unit blocking a large portion of the airflow. By changing to a larger high efficiency radiator you can correct the "problem". The Ford fix changes the condensor also.
In addition or as an alternate (this is what I have done) is to add a manual or automatic fan switch in parallel with the computer signal to the high speed circuit. I prefer automatic. I use a Hayden fan controller set to come on at 160*. (The computer doesn't turn the fan on till around 210*). I have also changed my coolant mixture to a 70-30 mix with Red Line Water Wetter added. This has allowed me to run open track events on 90+ degree days without heating problems. The nice thing about using a fan control unit is when tied directly to the battery, it cools the motor down after track session and then shuts off. With a manual you would have to remember to shut it off so your battery isn't drained.
BTW the Ford fix (which is a TSB not a recall) is 1200 +.
a Steeda or other radiator is 400 + some change.
the Fan controll unit is 50 bucks and some time. Water Wetter and a refill of the antifreeze mixed at 70-30. total around 65 bucks.