Level 10 tranny rebuilds

[Reaper450128]

I've asked this before in other parts of the site without getting to the answers I was really looking for, so sorry for the repost, but I'm going to ask again:

1. What different levels of rebuild do they do on our trannies? I've seen someone with a Stage III as I recall, and the price was a bit more than I'm interested in spending at this moment.
2. How much does each stage of rebuild cost?

I'd like to get the tranny I recently purchased rebuilt before I have the shop install it, because I want to be absolutely certain I won't have to do this again in a few weeks or months. If its in fully working condition now, and I am told it should be, then that should help lower the price of the rebuild... right? And before I go and do this, another question: the front and center differentials are technically separate from the transmission and therefore not required to be installed during a rebuild?