What should I do if I wake up on Friday in a state of major ritual impurity (janabah) and don't have enough time to perform ghusl? Should I perform tayammum to pray Jumu'ah?

One who is in a state of janabah must perform ghusl, and tayammum is not sufficient for them unless they cannot find water or would be harmed by using it. If one fears missing the prayer time by using water, the preponderant opinion is that they should perform ghusl even if the time for the prayer expires. If a person in a state of janabah prays Jumu'ah with tayammum, they must repeat it as Dhuhr.