1)
Why does it say "v'Tzara'as" with the prefix Vov?
1.
Radak #1: The Vov is superfluous, like I explained (refer to 4:41:1:1).
2.
Radak #2: It hints to omitted words. The money is given to you, and Na'aman's Tzara'as will cling to you!
2)
Did he curse his seed for all generations?
1.
Radak: No, he cursed only his three sons who were already born.
3)
Gechazi sinned. Why did Elisha curse also his sons?
1.
Radak: His sons knew about the matter. I elaborated [about a similar curse] in Sefer Shmuel (refer to Shmuel II, 3:29:2:1, 3:29:5:1).