Either the Roman Catholic Church is the ONE TRUE CHURCH established by Jesus Christ or no such Church and True Religion exists. However the evidence in this regard answers the question with absolute certainty for anyone really seeking the TRUTH.
If a seeker of TRUTH, and yet having more questions then answers, I recommend Fr. Walter Farrell's four volumes of : A COMPANION TO THE SUMMA (of St. Thomas Aquinas), starting with volume II which can be read or checked out online by doing a SEARCH on Companion To The Summa and clicking the proper link.
But for starters I say read the short article WHAT IS NEEDED FOR SALVATION at http://vaticaniidebate.com/id5.html.