I installed my garage door opener with a friend since my garage ceiling is very high so I needed some one to help me to hang the rail.
I replaced one side of torsion spring for my wooden(heavy) garage door myself and replaced a coil spring for my relative's metal(light) garage door.
All the tasks are doable but you have to do the homework before starting the real project.
You may ask your friends or get a professional to help you.