It is a one piece, I can tell you that much for certain. You will want something to tap the new one in with. I haven't found it yet but I think I can find some scrap pipe that will fit over the crank but just inside the outer diameter of the seal. On smaller seals you can usually just use a socket, but I don't have too many sockets around 4 inch.

Thanks for the tip madcat, I had thought of doing something simlar, cut or drill and then screw. At least I have the luxury of some time figure it all out. Only concern with cutting or drilling at it is making sure I get all the metal filings out before I put the new seal in.