ive now done quite a few diff rebuild/regear now an once you get the hang of it an get your head arround what your doing, then its pretty easy.
if its been a road car all its life, chances are it'll be fine just pull the diff out, replace the packs an shove it back together (obviously making sure they are set correctly by the book)
if the diff almost falls out instead of being a bit of a pull, then you'd need to have it set up, as chances are the bearings are worn and cos of the free play, so are the shims! otherwise just replace the clutch pack.
if you're going to set it up, you'll need the shim set, a DTI, and a micrometer, and prefferably the proper marking compound(dulux does work but isn't quite as effective) aswell as the guide to what are the correct an acceptable patterns.
don't let a landy person touch it or tell you he knows what he's doing, as they are compleately different to set up an a landy diff is probly the easyest thing in world to do!!!
its also not advisable to reset an already meshed ring an pinion as chances are you won't put it back to how it was, an it will prematurely wear out!