Christianity is a simple religion. Jesus is Lord and Savior and according to the Scriptures, one only needs to confess this to become a Christian. However, such confession must be from the heart. You must truly believe that Jesus is Lord and Savior. The mere repetition of such a prayer does not mean anything.
The Scriptures from Creation to Eternity all require a true belief or faith in God / Jesus. In the Old Testament this belief reflected a promise or promises made by God the Father to a person. The New Testament modifies this by making it clear that the promise to be believed is that Jesus is the Christ, the Lord, God in the flesh.
Such belief includes accepting the Virgin Birth, a sinless life, Jesus’ death on the Cross, and His Resurrection from the grave. Some conservative groups add a need to believe in a Pre-Millennial, Pre-Tribulation view of the End Times, but while this is true, I do not believe it is a necessary part of the prayer. However, it is clear that Jesus will return at some date in the future to complete the defeat of evil and sin, and such return is clearly a part of what Jesus accomplishes as Lord and Savior. Therefore, it will occur and it may be that while a direct belief in these events are not required for salvation, it is possible that a failure to believe in this position may mean that one does not truly believe in his hear that Jesus is Lord and Savior.