About the NT, I'm not an expert on it. But I do know, that today there are many different versions/translation of the original text. The original text however, is not any museum atm, but Muslims believe that in the future they will be revealed again, so there is no doubt about the truth.
This is a projection of flawed Islamic epistemology onto Christian revelation that absolutely does not work. To talk about the "original text" of the Bible, we must ask you first which book
you are claiming to be corrupted, and in what way. The Bible did not fall out of the sky one day, whole and complete with table of contents and authenticating watermarks or papers. It is a collection of books, and which ones make it into the canon and which ones do not can vary depending on the church in question. It is perhaps a bit more useful to compare it (albeit imperfectly) to the status of the Qur'an before Uthman's canonization of that text, where regional variant readings were commonplace (e.g., Kufa had its own reading that differed from other places). Even churches which are in communion with each other (such as the Egyptian church and the Armenian church) may not have exactly the same canon, but neither says of the other that they do not have the "true" or "original" Bible, because the faith that they hold to is the same, brought to them by the apostles who predate the canonization of the Bible
in any one particular church.
This is the problem in Islam's form of self-knowledge and acceptance of revelation, from a Christian perspective: In Christianity, the revelation to and salvation of man is through the Word made flesh
in the person of Jesus Christ, with the Bible flowing out of that experience of God among us. In Islam, by contrast, there is no incarnation and hence the revelation is through the written text of a book
. This would be much less strange to us if Islam didn't then turn around and call us "People of the Book" (we were people of God
for centuries upon centuries before "the Book" was ever canonized), while also chastising us for our supposed but unproven failure to preserve our Book, all because we did not do as Uthman did and create a redacted version which we would then be seen as "the original" (when in fact that is not a problem, because for the Old Testament we have had the LXX since before the incarnation of Christ, and the New Testament is at least
the 27 books first declared canonical by St. Athanasius the Apostolic several hundred years before Muhammad or Islam existed, which is still what you'll find in the Bible today).
Please do more study into the NT and its canonization before deciding that the common Islamic viewpoint on it is the correct one by default. We are dealing with two completely different systems of revelation and preservation, and for all the supposed uniformity (~ authenticity?) guaranteed through yours, ours has proven no less reliable in the face of higher textual criticism (the type of which Islamic orthodoxy has not allowed up until this day; cf. the Sana'a manuscript), and with far less destruction of period texts than Uthman's method (i.e., non-canonical gospels and other writings such as those of the early Church Fathers were preserved as sources of tradition in a way that might be familiar to you if you keep to sahih hadith -- they're not considered on the same level as the Bible itself, but they provide us with glimpses into the lives of the early Christians, so that we know, for instance, that the Bible that we have today is the same as that of the early Christians, and our services have preserved their practices, etc).