Christian baptism - Catholic teaching

At school (Roman Catholic) in Religious Education classes we were taught that only those who had undergone a Christian baptism had a chance of entering heaven. All others, even if they had led exemplary lives (in Christian terms, of course) could only hope for eternity in Limbo, at best. It was so important for everyone to be christened that Baptism was the only one of the 7 Sacraments which could be administered by any other person, even a child. In fact it was a DUTY to administer such if the imminent death of the 'subject' was expected and no priest was at hand. This I took to have been the Church's teaching since time immemorial. Now I read in the 'Catechism of the Catholic Church'(1994) that "For (those) who die before their Baptism, their explicit desire to receive it, together with repentance for their sins...assures them the salvation that they were not able to receive through the sacrament." So were we taught incorrectly then? Since the doctrine of Limbo was, for all practical purposes, 'ditched' earlier this year I suppose there had to be some 'tidying-up' of inconsistencies, but I'm left more than a little confused - and this is just one example of a myriad of oddities that were pumped into our young minds when we were too immature to challenge them. But who says the Catholic Church doesn't move with the times? - (Me, for one) - but when it does it's only at the rate of continental drift. I look forward with bated breath (NOT!) to a revision of the teachings on artificial contraception, celibacy of the clergy, ordination of women, divorcees marrying again whilst former spouses are still alive - and, of course, homosexuality. (By the way, please don't anyone bother to tell me that it won't affect me anyway because I'm going to burn in hell for eternity. Wow, the prospect scares me shitless!)