Disconnect the garage door opener
Close the garage door fully
Clamp locking pliers on the track to keep the door from moving
Unplug the opener
Identify the spring type: torsion spring or extension spring
Gather the correct replacement spring and proper tools
Release tension from the old spring
Remove the old spring hardware
Install the new spring in the same position
Reassemble all brackets, cables, and winding components
Apply the correct tension to the new spring
Tighten all set screws and fasteners
Remove the locking pliers and test the door balance
Reconnect the opener
Test the door operation several times
Call a professional if the spring system is damaged or if you are unsure