A bit more than a basic reclading, I think they were able to retain the core of the building and foundation and little else.
All the services and floors and lift shafts/fire safety ducts are new.
If you look at what was done with the building at the corner of Tara St and Pearse St it would have been a similar if not more comprehensive undertaking.
The cladding was the easiest part, and although I don't like the stone selected or the window materials. I do concede that the drawings and resulting form is good if not the materials.
It was for its time an exceptional project hwen you think of the other commercial developments of its time.