I guess i will point out that he has a 4L60e trans and says it is stuck in 2nd gear.. the default gear on a 4L60e is 3rd gear as pointed out in the TSB that was posted too.
Default on the 4L80e trans is 2nd gear.
Perhaps the vehicle owner does not know what gear the trans is stuck in? Lets hope he finds the problem easily
Dont worry how old you are... it is the mileage on your body that adds up.