Garage door torsion spring replacement will be required eventually, usually after one breaks. Before you attempt to try to replace these on your own, there are some words of caution.
Just because you may be handy with some tools and do a little tinkering around the house, doesn't mean you should just go for it when it comes to this particular job. These springs are under high tension, and even if the spring itself is broken, if you have a double garage door, the other spring needs to be loosened before you even attempt to replace the broken one.
Tightening the new spring is a delicate process, and not doing it right can cause serious injury.
Garage door torsion spring replacement is a little complicated, so if you think you want to try to replace it on your own, you should really do some online research first. There are DIY resources that can walk you through the process step by step, and you should find the three most comprehensive sites to walk you through the process.
Again, this is where you should really think about your skill level. You should read the instructions thoroughly, especially when it comes to the potential dangers and think about if this is something you want to do on your own. While it may cost to hire someone, unless you are absolutely sure you can do it, you should have someone who knows what they're doing (a professional) come in and take care of the problem.
One of the things you may have a bit of difficulty with is finding the torsions spring and the parts involved in order to do it on your own. You should really look in your owner's manual to find out what the parts numbers are for your particular model. If you own an older model garage door, or didn't get a manual when you purchased your home, then you are going to have to look over the spring and housing itself to see if you can find a number stamped on it somewhere. Of course you can always take a picture of it with your digital camera.
The real first steps to garage door torsion spring replacement is safety precautions. Look over your instructions carefully, and make sure that you have all the tools you need. It is never a good idea to substitute a torsion spring adjustment bar with a screwdriver; you could seriously injure yourself. Never use buckets to stand on, always use a ladder. Make sure that you have safety goggles, and use them.
If you can, download the DIY manual you have chosen off of the internet, print off a copy, and use it in the garage so you don't have to keep going back to your computer, and can get the job done faster. One of the most important tips you can have during garage door torsion spring replacement is to take your time, follow all the instructions to the letter, and remember to be safe.
Warning: This job is extremely dangerous and is known to have caused many injuries and death. Proceed with extreme caution. Better yet, call a professional.
Some excellent websites that provide comprehensive instructions are http://ddmgaragedoors.com/diy-instructions/replace-garage-door-torsion-springs.php, ( this is by far the better guide ) and http://www.ehow.com/how_4724496_replace-garage-door-springs.html ( instructions are not great but included in case the other site is down ). Both of these sites are completely free.