What is the mening of "v'al Safam Ya'ateh"?
Rashi: It means that the Metzora must cover his head down to his moustache like an Aveil. 1
Targum Yonasan: It also means that he must keep outside the border of the town. 2
Why did he have to call out 'Tamei Tamei'?
Rashi and Targum Yonasan: To warn people to keep away from him, to avoid becoming Tamei by touching him.
Moshav Zekenim: He must announce his pain to others, and they will request mercy for him. 1
Moshav Zekenim: One whose entire body is covered with Tzara'as, everyone knows this, and he need not announce; he is Tahor. (People do not see under his clothes, only exposed areas. Also one whose face and hands are covered with Tzara'as, everyone knows this! - PF) Similarly, a snake is totally covered with Tzara'as, therefore it is not Tamei like other Sheratzim are.
Why is "'Tamei" repeated?'
Mo'ed Katan 5a: This enables us to learn two laws from this. Tum'ah announces itself, i.e. one must mark off graves 1 , and a Metzora announce his pain to others, and they pray for him.
What do we include from "ve'ha'Tzaru'a"?
Moshav Zekenim: This includes a Kohen Gadol, even though it says "u'Vegadav Lo Yifrom" [regarding a Mes, he tears if he gets Tzara'as].