I'll try to help as much as possible, let's see;

Yes on the cups or whatever they are called.

The ring gear is held on with bolts, it should come off pretty easy.
When I was watching mine and jeff's being put on, the gear just lays on the posi unit and the the bolts hold it on.

You'll have to get the new bearing on the unit pressed on, if i remember correctly.

On the shims, you should be ok with the original ones, just make them or make note.

Replace that crush sleeve, the rest of your stuff should be ok since you only have 30K on the truck


good luck,

allen