Cut your losses now. There are plenty of other great paying jobs within the railroad other than the high iron.
You work in the yard you'll stress your back and legs walking, climbing, pulling, lifting, etc. Work as an engineer in the yard and you'll subject yourself to plenty of hard joints (couplings) again causing stress on your body.
You work on the road from terminal to terminal you'll stress your body given the amount of rough track and poor riding motors not to mention having to carry your two/three bags of books, clothes and other "required" gear to and from the shanty to the motor, climb the ladder up to the motor with your grip, from the motor to the van that takes you to the hotel and vice-versa.
You can give it a try but you may find yourself cussing at doing so. It's a tough gig. Good luck.