Salvation in itself is very easy....
8 ....The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;
9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. - Romans 10:8-10
From there one must grow his faith.
Salvation is not as easy as you think. Jesus said that the way to eternal life is narrow and few there be who find it. Yes, it is easy to walk up to the front of a church and say a prayer, and believe the Scriptures you have quoted. Even the devil and his demons believe those Scriptures. Easy believerism is just the act of getting religion and putting on a Christian badge, without one's heart being changed.
Thousands upon thousands made decisions for Christ in Billy Graham crusades around the world, but very very few of those converts ever went and bonded into a church, and so there is no assurance that the majority of the ones who went forward got actually saved.
There is a Scriptural progression for salvation:
1. The person needs to be measured up against God's moral Law, and see himself as totally failing to keep it. The purpose of the Law is to show us how sinful we are, and that we are guilty according to the Law and subject to the penalty of God's eternal wrath and hell. That is the bad news. Unless we know the bad news, we won't really appreciate the good news.
Too many make decisions for Christ without knowing the terrifying state they are in and that they desperately need Christ to be their Saviour. This is the difference between genuine Christianity and churchianity. I have a background in the Pentecostal movement and I have seen many join up for the goodies, goosebumps up the spine, miracles, guaranteed healing, prosperity and the prospect of meeting an attractive prospective wife. Just imagine the rude and terrifying shock that many of these will get when they find that they have risen from the grave in the wrong resurrection, and they are resurrected to face the Judgment, instead of the rewards that Christ will give to His faithful servants.
This is the honest and true gospel.
This is why the way to eternal life is narrow, because relatively few come to Christ through having been convicted of their absolute sinfulness and have come to Christ with all their hearts to be rescued from the terrifying prospect of hell. They know they have to flee from the wrath to come and to take hold of Christ and not let Him go until He blesses them with saving faith.