Swapping a single bottom panel yourself is possible if the door is unplugged from power, the spring tension is released safely, and you can get an exact match section - the part most DIYers underestimate. Where it stops making sense is torsion spring work: on a cold-climate steel door, a spring under load that lets go can break fingers or worse, and that's not a repair to learn on your own garage. If the panel damage is limited to cosmetic dents with no bent track or hinge, a patient homeowner with the right tools can do it. If the door binds, drags, or the opener strains to move it, that's a sign the frame shifted and it's past a panel-only fix.