Roger Shoaf writes:

Open the door partway so the lower section of the track can be
unbolted and then you can probably flex the door enough to slip out
the old one and slip in the new one.

That is FOOLISH DEATH-WISH ADVICE. Follow it at your peril. Sectional
doors cannot be safely disassembled by the casual do-it-yourselfer.

Besides, the OP doesn't even specify the bottom seal or an inter-panel
seal. It matters.

http://www.truetex.com/garage.htm