TO be honest, they hardly ever break anyway. The salisbury has been in use since the series 3, and has hardly caused any problems in its function.
You'd be better using a piece of metal rod, about 10mm diameter, and just push it through (or hammer it) to knock out the broken piece of shaft, if it ever comes to that.
When I fitted the ARB locker to the back of my 110, the diff unit more or less came out on its own anyway... any axle with a good amount of miles on it would have loosened up, so with the aid of a couple of levers, you should be able to get the diff out. My friend who did the ARB fitting with me, had a huge set of G clamps that fitted around the casing, this helped a little bit too. but I woudln't worry personally.