So I am going to suggest that you buy and read a few books. Then, Karl Keating, Catholicism and Fundamentalism . Then Frank Sheed, Theology for Beginners . Another good book is Catholicism and Reason by Hayes, Hayes and Drummey. The bath of rebirth is baptism.
Grace is necessary for salvation.
Christ instituted the sacraments as the ordinary means by which he confers on us the saving grace he won for us on the cross.