To replace the door panels, the doors have to be taken completely apart. You will need to take the doors off and set them on the floor or a table. Lift the gasket and you will see the screws holding it and the inner panel in place. Remove the screws, all the way around the door and then lift the inner panel and gasket off of the outer door panel.
Putting this back together will be more difficult. Lay the inner panel back in place, on the new outer panel and also the gasket retainers without the gasket. Now put all the screws back in place but don't tighten them down yet. Now the gasket has to be put back in place, with the lip under the retainers. When the gasket is completely back, now you can tighten the screws. Reinstall the door assembly now and if it does not close good, you will need to loosen all the screws again, so the door can be adjusted properly. The inner panel holds the door in the proper position. When the door closes good, all the way around, now you can tighten the screws again. This can be a difficult job and I recommend having a technician do this.