Mike I'm not sure we are talking about the same spring, this is the large one that is over the door, I've seen smaller ones that go elsewhere, (Image removed from quote.)Home depot sells some smaller ones that I think go on the sides in some instances.This thing is very big, and thick steel that has to be set to a tension with special bars, kinda tricky, but like Zoid said just need to take your time.
My dad did it for me...And I wasn't even at home when he did
Sounds overly reasonable...