The truth of salvation has been confirmed to me by reading God's word.
I am the resurrection and the life. He who believes in me will live, even though he dies." John 11:25
Seeing a miraculous sign or would definitely help establish the truth of Christ's ministry. Look at all the example in the Bible of Kings and others who didn't believe going out and proclaiming the Word of God after experiencing a miracle. Daniel's king, Shadrack, Meeshack, and Abendigo's king, Paul, Daniel's king, there are so many instances.
I've formed my opinion of the value of signs from the entire Bible. I lean towards the New Testament because of the manner of the miracles. But I believe and trust in the entire Word of God.