I would say new bearings and seals is usually a good idea, cheap insurance. Are you going to setup the gears yourself or have a shop do it? Since an ARB is a full carrier locker you will have to set the pinion depth and backlash and all that stuff i don't understand, lol. Using the same shims will get you close, but not perfect. From what I understand its not a terribly difficult process, just very time consuming, and you need some special tools. At least you can put the diff on a workbench though to do it.