Even within Jesus own apostles there were differences, most of the time they didn't even know what Jesus was telling them, along comes Paul years later and he is doing stuff that they didn't even know was suppose to be done and they had to get everyone together and discuss it.
Change is inevitable, but as long as the core ( in this case faith) of something (in this case religion) remains the same, differences of opinion in regards to things can be worked out, or at least should be.
While the faith that the majority of christian have is the same as it was 2000 years ago, the doctrines have changed, rules and restrictions were added, dogma was developed, divisions resulted, denominations were created, but in the end, the faith ( for the most part) has remained unchanged.