As to the Exhibition rebuild, see
http://www.nipperhead.com/old/rep_exhib.htm .
If I had had this resource earlier, I would have attempted my own rebuild. But to answer your question as to what/how much to replace: definitely the front gaskets and the back flange (see
http://www.rmrmfg.com/phono.html). Others can recommend sources for the diaphragm gasket material; as I said, mine was rebuilt by Victrola Repair Service (
http://www.victrolarepairservice.com/index.html), and the stuff they used then was absolutely tops! Maybe they will sell you enough to do the job; it's *very* pliable, which is the most important quality IMO, and it's made all the difference in mine. As far as I can tell, they did not replace the diaphragm, which to my eye looked OK when I sent it out: no visible cracks, etc., so yours may by OK. If so, don't fix it. Finally, you will need beeswax to reseal the needle bar where it contacts the diaphragm; this has been discussed on the former board, IIRC, and the concensus is that the best kind to use is brown, as opposed to yellow, in color. I obtained a small bar of this at a local craft outlet. Finally finally, if you need needle bar springs or needle screw, try here:
http://www.antiquephono.com/ . They have other sound box parts in their catalog, too. Good luck, and let us know if you need help; in particular, the needle bar adjustment, while not all that difficult, can be tricky. Post here when you get to that part.