It's not taken totally apart, but it is stripped of the interior down to the bare metal, all wiring is checked/replaced as needed. All mechanical parts like the flaps and landing gear are removed and checked for wear. The skin is checked for cracks. This is done every 5 years for planes, taking about 5-6 weeks to complete.
How is that safe unless you've got a production line doing it? Seems impossible to re-assemble it in the same way as it was done in factory...