we did this just few days ago on a Facnor furler
, which basically the same as profurl (in fact i think profurl now own Facnor - our nw swivel is a profurl, and a much more substantial piece of kit too !)
anyway, the riggers who did the work
removed the drum and put the new swivel on from the bottom. did not take long...2 guys who obviously knew what they were doing did it in about half an hour
naturally took a couple of halyards down to the bows to restrain the mast
when forestay was released, and we all prayed hard that all bolts etc came out without stripping / snapping (they did). otherwise, just follow the process
good luck !