When I was LDS, I believed (like I was told) that many "plain and precious" parts of the Bible had been removed by corrupt and careless men. Among these missing "truths" was the Mormon Gospel.
Now that I am a Christian, I have more faith in God's ability to preserve His word, and with good reason. For example, I've just started a new Bible study, and, by Genesis chapter 4, have already come across the real gospel (1 Corinthians 15:1-4) 4 times! Wanna see?
#1 - Genesis chapter 2 -
God has created Paradise for Adam and Eve; everything is beautiful, wonderful, and freely provided for them. They also have complete liberty, except for one thing. God has planted two special trees, and while He says they may partake of the fruit of the "tree of life", He has expressly forbidden them eat from the "tree of the knowledge of good and evil".
What is the "knowledge of good and evil" but the knowledge of right from wrong? When we were babes, we were innocent; once we understood right from wrong, we were responsible for the consequences of willfully choosing the latter. God didn't want Adam and Eve to perish (Genesis 3:16-19), which now they would do, the consequence of not being able to live according to His righteous standard.
At the cross, Jesus took upon Himself the penalty for our wrong doings, if we would do what? Choose Him -- the One who hung on the tree for us (1 Peter 2:24) -- Life. In the Garden of Eden, God's free gift of salvation (eternity in His presence with all its benefits) was the choice they could have made. It is the same gift offered us in Jesus Christ (Romans 6:23, Revelation 22:14)
#2 - Genesis chapter 3 -
Adam and Eve, having then chosen to disobey and discovering their nakedness, hide their shame with leaves. God’s response is to kill an animal, prepare its skin, and then exchanges their leaf-covering for the covering that He Himself has provided. Reading through the books of Moses, we see God set up a system of unblemished-animal sacrifice among His chosen nation, Israel, just to point them forward to the time when His pure and sinless Lamb, Jesus the Christ, would shed His blood for our sins. God took from Adam and Eve their own attempts to be found "covered" in His eyes by something that they could do (works), and covered them with a foreshadowing of the only thing He can accept as payment for sin - Jesus.
#3 - Also in Chapter 3 -
The "serpent" responsible for beguiling Eve (2 Corinthians 11:3) is cursed by God. God says, "I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel." The seed of the woman, of course, is Jesus (Galatians 4:4). At the cross, the adversary bruised the heel of the seed of the woman when Jesus died, but our Savior dealt the head-crushing blow, arising from the grave triumphant over Satan, death, and hell (Isaiah 53:10, Acts 26:23, Hebrews 2:14-15).
#4 - Genesis chapter 4 -
Cain offers up the fruit of his labors and Abel offers to God a sacrifice from his flocks. God accepts Abel's offering, but not Cain's. Why not? Again, because the only sacrifice that is pleasing to God is Jesus, or one that shows understanding of the nature of perfection of Jesus' atonement. God is not pleased with the fruits of our hands, our works, apart from Christ (John 6:29, Romans 4:2,6)! Abel, it seems, understood this, but Cain did not.
God's "good news" for us is that despite our wretchedness, Jesus' atoning blood covers our sins, and we can once again be united with God. The idea that the "true gospel" has been removed from the Bible is simply is not realistic. The one and only true Gospel, Jesus and His perfect work on the cross; His triumph over death to save us, is IMPOSSIBLE to remove from the Bible! As you can see, it is written into to the details of the human story by Almighty God, right from the very beginning.