I was looking into it a while back (settled for another plug and play radio instead). Essentially, you need a deck that is Sirius compatible. That means it will show the song titles, artist, and all that.
Behind that, hidden in the dash, you need 2 things: the Sirius universal tuner (includes the antenna and the "decoder" for the antenna) and an interface that essentially translates between what the antenna receives and your deck. That interface is specific to the deck brand, be it Sony, JVC, etc.
This takes care of the first 3 items on your list. The "satellite radio" has no business there and the installation is self-explanatory. As for the other two (harness & kit), I don't have a clue. Probably something extra they use during their own installation as a mean to make extra money. As far as I know, someone who does this installation themselves don't have anything extra such as these to purchase.