Garage door springs generally have a lifespan of 10,000-20,000 uses. They're one of the parts of the garage door that generally doesn't fail, but when it does, it needs to be fixed ASAP or the door won't operate as it should.
Still, even though it may look simple, garage door spring repair is something that should definitely be left up to a professional. There are videos online that can show you how to properly replace the spring, but it's one of those jobs that can go wrong in a hurry for the following reasons.
Torsion springs are under an extreme amount of pressure. This tension helps raise the garage door — which means it's relaxed when it's in the open position — but if it's fiddled with while under pressure, it can snap and cause injury or even death. Most garage door springs have safety cables that catch the spring if it collapses, but it's still dangerous. If for no other reason on this list, you should let a garage door spring repair professional handle it for the danger factor alone.
It Takes Special Tools
Even if you have a toolset that is the envy of every other person on the block, chances are you won't have the highly specialized equipment that is necessary to repair the door. Garage door spring repair takes more than a socket set and a screwdriver, and more than one homeowner has ended up injured or disfigured as a result of a broken spring. It's much cheaper and safer to let a professional handle the repair.
It Could Get Worse
The possibility of death or disfigurement is always present when working on a garage door spring, but even if that doesn't happen, there's still the chance that any repairs that are performed actually makes the situation worse. In many cases, a homeowner won't notice the problems right away but will notice it when they try to resell the house at a later date and an inspection points it out or when the garage door suddenly breaks on them. If that happens, you'll have to contact a professional to come out and replace it anyways, which is even more time and money out of your pocket. It's much better to let someone who is skilled in handling these types of situations fix it first, rather than work on it yourself and make the situation even worse.