Highly doubt you will be dequal for a surgery. Long as your doctor will sign off on you, you will be fine. Its not a severly physical job as they explained.
From what ive heard from multiple lirr employees in the same department. S&d is the hardest thing you will be tested on and marks if you are actually trying for the position. Thats the whole point of it being pre employment. They arent just taking anyone, you need to put the time in....