While a nonprofessional can install a garage door, it's often better for a professional to do the job to ensure the door is installed correctly and operates safely. If installed incorrectly, a garage door can come down with enough force to severely injure someone.
Professionals also help a homeowner select the right door. A garage door professional should be a member of the International Door Association, be well experienced, provide references, adhere to the most current regulations and codes and have up-to-date insurance. If a homeowner does decide to install the garage door, an experienced professional should inspect the work.