See the Sectional Overhead Garage Door catalog (PDF file) from the Prime-Line replacement hardware company. Their brochure Sectional Garage Door Torsion Spring Installation Instructions (PDF file, part number GD-12280) is brief but informative. Apparently you can only obtain their torsion springs as special order items through mom-and-pop type hardware stores like Ace and True Value, and not the big-box Home Depot and Lowes.
If the wires that run from your opener to the photo eyes and to the wall button are exposed, replace them, too. Those wires have probably been in your garage for 10 years or more, and they may be nicked or worn. Newer openers are extremely sensitive and won’t work if a wire is damaged. It only takes about 15 minutes to run the new wire, so it’s time well spent. If the wires are protected inside the wall, you don’t need to run new wire.
And for some extra features, you'll appreciate accessing the system through the MyQ smartphone app. You can set up this Chamberlain opener to automatically close the door after 1, 5, or 10 minutes, which is great for people who are a bit forgetful. We also really like the motion-detecting control panel, which turns on lights whenever it records nearby movement.
Garage Door Repair