There are two types of garage door springs Torsion and Extension. Torsion springs are attached just above the garage door, while extension springs are located above the upper track on both sides of the doors. Extension door springs also should have a safety cable that runs through the springs to help hold the garage door should the spring break.
Keep in mind that garage door springs are tightly wound and under a great deal of tension, after all they holding up a 400 pound door, that can come crashing down seriously injurying or killing you or a member of your family.
Garage door spring repair should never be done by a non-professional due to the dangers and the risk involved should something go wrong.
For example an older garage may not that the height for a roll up or swing up door, and may not be able to accommodate a slide to side door, leaving you with having to settle on a swing out door. Of course if your previous garage door is a swing up, roll up or slide to side door then you can choose the same type of door again.