Hasn't time proven that Protestanism always leads to Heresy

[nhylan]

Jesus said:

"But when he, the Spirit of truth, comes, he will guide you into all the truth. He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come. He will glorify me because it is from me that he will receive what he will make known to you. All that belongs to the Father is mine. That is why I said the Spirit will receive from me what he will make known to you.”

Leaving the Catholic church out of it for the moment, where can one go, in the protestant sphere, to find “all truth” via the guidance of the holy spirit?

Your question isn’t one that a Protestant would answer in a way that you would find satisfactory. Your question assumes that there is a Church where one can find ALL truth. All mainline Protestants would reject that premise outright. I’m not sure I’m right on this but doesn’t the Roman Catholic Church teach that even it only has all truth necessary for salvation?