Gavin ,
I do not think you will have to remove the differential to do this job . Do you have the KT3 manual on this ? I think it can be done by removing the firewall and steering levers . Let me take a look in my book and i'll get back to you on this . I have my unit completely out of the sno cat as we speak .
If nothing else i'll go out and pop the inspection cover off mine , to see what is entailed to do this ,as it needs to be done anyway before being reinstalled .
This would be a great "How To Install Brakes" article for other Kristi owners so lets get pictures too and post for everyones benefit !!!
EDIT: I just checked my manual and the Brake Band replacement procedure is explained on pages 6 & 7 . YOU DO NOT NEED TO REMOVE UNIT !