Just had a torsion spring go on a double car garage door. I did all the reasearch and knew how to measure and get all the info, but when I priced the springs and would be at $100, just for springs I called and got several quotes and they went from $190 to $400. I called the $190 guy and he was here in 30 minutes, took 2 hours, and away he went.
A couple interesting things were: a) He replaced the springs with the door in the up position, which meant no pressure on the springs. He said he always did it this way becasue it was much, much safer. I watched and it was.
b) He carried springs in 10' lengths in his truck and then just cut them to the exact length. Put new end caps and hardware on and reassembled everything.
I do alot of things myself, but this was not one I really wanted to tackle from what I had read, but watching him do this with the door in the up position sure made a lot of sense.
I commend him on how he disconnected all power sources, clamped the door to make sure it did move, and wore glasses. Very professional and nice guy.