John MacArthur recently preached from Mark 16:8-20, , making it the last sermon in his 43 year ministry in which he has preached all the way through the New Testament, verse by verse, book by book; a great model for expository preaching. (exposing the meaning of the text, in its context, preaching through each book from beginning to end, verse by verse, chapter by chapter.) I highly recommend his other sermons, all available there at www.gty.org
He gives a good summary of the confidence we have from all the many extant Greek manuscripts that we do have about the Bible, specifically focusing on the New Testament; and by comparing all of them, we can tell where a scribe made an error or added something in (as in Mark 16:9-20; I John 5:7-8 (KJV) - "the Comma Johannine"). No textual variant affects any doctrine in the word of God, the Scriptures.
A good introductory book on the reliability on the NT is F. F. Bruce's The New Testament Documents: Are They Reliable? He answers yes.
"I like Mark's ending!" John MacArthur (speaking on verse 8, where the women are amazed, trembling, astonished, and afraid at the empty tomb and the resurrection and what the angel said to them.)
Verses 5-8 are key, and include the amazement, the crucifixion, the empty tomb, and the angel's statement: "Do not be amazed; you are looking for Jesus the Nazarene, who has been crucified. He has risen; He is not here; behold, here is the place where they laid Him."
Whatever criticism Muslims and skeptics and atheists have about Mark 16:9-20, the crucifixion and the resurrection are still affirmed as true, even without verse 9-20. Chapter 15 - Crucifixion, 16:1-8 - Empty Tomb, resurrection, women who are eyewitnesses of the empty tomb. "He has been crucified." This is historical fact. The Qur'an has that embarrassing verse of 4:157 of denying historical fact.
MacArthur has a great approach to handling the long version of Mark, 16:9-20, and that this section is not in the oldest extant Greek manuscripts. He shows how verses 9-20 were cobbled together from the other 3 gospels and Acts, and added onto Mark.
v. 9 - summary from Luke 8:1-3
v. 10 - from John 20:18
v. 12 - summary from Luke 24:13-32
v. 13 - from Luke 24:36-38
v. 15 - summary from Matthew 28:19
v. 16 - different way of saying John 20:23
v. 17-18 - from Luke 10, Matthew 10, tongues in the book of Acts, and Acts 28:3-6 (God protected Paul from the harm of the snake bite; but there is no text of anyone drinking poison as in Mark 16; and there is no command to pick up snakes in a worship service context as they do in some churches in the Appalachian Mountains of USA. )
I would add this about the summary of verse 19. McArthur points out that Irenaeus quoted Mark 16:19 around 180-200 AD.
v. 19 - John 20:17; Luke 24:51; Acts chapter 1; Luke 22:69; Acts 7:55 ff; Romans 8:34; Ephesians 1:20; Colossians 3:1; Heb. 1:3; Heb. 8:1; 10:12; 12:2; I Peter 3:22; Psalm 110:1)
MacArthur focused on verse 8, the Amazement, astonishment, fear, and being astounded all through the book of Mark: (which points to the probability that that was Mark's real ending.)
MacArthur ends with joyful exuberance quoting from the hymn: (text and music by Charles H. Gabriel)
"I stand amazed in the presence of Jesus the Nazarene, and wonder how He could love me, a sinner, condemned, unclean! O How wonderful, O How marvelous, and my song shall ever be, O How wonderful, O How marvelous, is my Savior's love for me!"
Indeed, Jesus is Amazing!