Yes front diff has to be dropped completely, I find it easier to drop it complete with front x member, it drops a whole lot easier and gets round the pig of a job lining up the front mounts when putting it back, only problem is the four bolts are in from the rear two come out OK but the other two need to be loosened off, pushed back and the bolt head ground off with a mini disc cutter, then replace them from the front with 2 new high tensile bolts.
You do not need to remover the calliper to drop the diff but if you are doing the brakes then yes they are standard thread, I use a 3ft breaker bar, Rick