[Elentari_Elbereth]

This is such an interesting thought, and one I have thought of often.

I know the Fellowship would probably not have split up as it did, and all the other events trailing from it would never have happened.
If gandalf never came to Rohan, Theoden would still be under control of Saruman, and the whole country may have been conqured... And if Aragorn never went through the Paths of the Dead, surely Gondor would be destroyed, and not to mention no help from Rohan.

My thoughts are, if the Fellowship and Gandalf stayed together and proceeded to Mordor, would they have been able to destroy the Ring before Sauron could destroy Man?
Could they travel through Mordor quicker as 9? or would it be more difficult because they could be spotted easier?

Also, would Gandalf still have became White even without dying?