How difficult is it to change garage door springs?

Changing garage door springs is considered a very difficult and extremely dangerous job for a homeowner, not because it requires many tools but because it involves extremely high tension that can cause severe injury or death if done incorrectly. Torsion springs above the door store hundreds of pounds of torque, and you must use special solid steel winding bars that fit precisely into the winding cone, not screwdrivers or other substitutes, to wind and unwind the spring. The process requires carefully releasing tension from the old broken spring, loosening set screws, removing the old spring from the torsion tube, installing the new spring with correct wire size, inside diameter, and length matched to door weight and height, and then winding it with a specific number of quarter turns, typically 30 to 36 quarter turns for a 7 foot door. If a winding bar slips, the spring can unwind violently and strike you. Extension springs are slightly easier but still under high tension and require safety cables. The difficulty also lies in correctly sizing springs; if you install the wrong size, the door will be unbalanced, will not stay open, will strain the opener, and can go off track or damage cables. For these reasons, professional replacement is strongly recommended and costs 200 to 400 dollars for one spring and 300 to 600 dollars for a pair.