Yoma 73: Light and Truth

On the kohen gadol, and his colleague, the kohen who is anointed for war (mashuach milchamah). The kohen gadol is excepted from certain practices, specifically with regard to mourning, because of the importance of his office and how he represents it. Also, who is the mashuach milchamah, and how does his role fit into our understanding of the kohanim? Also, the Urim ve-Tumim -- how does it work? How does one ask it for counsel? And how does it answer?