First thing is to understand the principles of how these doors
work. See my essay at:
http://www.truetex.com/garage.htm

I bet you spent longer on that essay than it took to repair your garage
door. Say, my 17 year old torsion door needs retightening for the umpteenth
time. Needs it every year now. Its the really standard 7'x16' door. Is
there really no way to order a replacement without unwinding it?
Karl