Re plugs:
It will cut the patch to the same size and shape and drop it into the space as a plug. The tiny gap around the patch will be filled with paintable sealant that will stretch and compress as the fuselage is pressurized and unpressurized.
Then mechanics will work on the inside, gluing a splice plate to the original skin and to the patch, overlapping both by about 4 inches.
I thought the above stated that they are plugging it from the outside. Did I misinterpret the description? "Drop it into the space" etc...