I would have thought that even an ex-JW would have difficullty accepting teachings like celibacy, immaculate conception and papal infallability.
Well, I'll partly respond to Chappy. First of all, celibacy is only mandatory in the Latin rite of the Catholic Church. There are 22 Catholic Churches in communion with the Bishop of Rome. Eastern Catholic, such as those in the Byzantine rite, priests can get married and then they can be ordained. Its a matter of discipline rather than doctrine.
Papal infallibility stems from Matthew 16:18. There is some discrepancy between ho petros and he petra in the Greek and personally I've never seen that sufficiently explained. But we must remember that the bible is not the sole source of doctrinal information, for even John says in his Third Epistle: "I had many things to write, but I will not with ink and pen write unto thee" (3 John 1:13 KJV). It can be deduced from this and other sources that the Bible is not the sole source of information for Christians, especially considering that the Bible as we know it was not formed until around the 3rd century (? - sometime around then). Here's how Catholic.com explains it:
In this discussion it is important to keep in mind what the Catholic Church means by tradition. The term does not refer to legends or mythological accounts, nor does it encompass transitory customs or practices which may change, as circumstances warrant, such as styles of priestly dress, particular forms of devotion to saints, or even liturgical rubrics. Sacred or apostolic tradition consists of the teachings that the apostles passed on orally through their preaching. These teachings largely (perhaps entirely) overlap with those contained in Scripture, but the mode of their transmission is different.
The Feast of the Assumption, another Marian Dogma, has been around since the 7th Century and the Orthodox Church also celebrates this feast and dogma. Papal infallibility, as defined at the First Vatican Ecumenical Council, simply means that when the Pope, making a statement as the Pastor of the whole church, defines or makes a declaration on a matter of faith and morals, he is making that statement infallibly.
The interesting thing is that when you read the writings of the first Christians, you realise how utterly Catholic they sound. Many say that baptism by sprinkling is unscriptual, but in the Didache we found written: "... pour water on the head three times in the name of Father and Son and Holy Spirit" (Didache 7:3 - trans. ed. Ehrman, Bart. D. The Apostolic Fathers. Harvard University Press: Cambridge, Massachusetts, 2003). The context is that the text is explaining that you should baptize in running water, but if don't have that use cold, but if you don't have that use warm, and if you don't have that "pour water..."
Yes I did have difficulty accepting many Catholic dogmas, but I just had to deprogramme my built-in prejudices and WT ideas.