The New Testament specialist Daniel Wallace notes that although there are about 300,000 individual variations of the text of the New Testament, this number is very misleading. Most of the differences are completely inconsequential--spelling errors, inverted phrases and the like. A side by side comparison between the two main text families (the Majority Text and the modern critical text) shows agreement a full 98% of the time.[18]
Of the remaining differences, virtually all yield to vigorous textual criticism. This means that our New Testament is 99.5% textually pure. In the entire text of 20,000 lines, only 40 lines are in doubt (about 400 words), and none affects any significant doctrine.[19]
Greek scholar D.A. Carson sums up this way: "The purity of text is of such a substantial nature that nothing we believe to be true, and nothing we are commanded to do, is in any way jeopardized by the variants."[20]
This issue is no longer contested by non-Christian scholars, and for good reason. Simply put, if we reject the authenticity of the New Testament on textual grounds we'd have to reject every ancient work of antiquity and declare null and void every piece of historical information from written sources prior to the beginning of the second millennium A.D.
Has the New Testament been altered? Critical, academic analysis says it has not.
[18] Wallace, Daniel, "The Majority Text and the Original Text: Are They Identical?," Bibliotheca Sacra, April-June, 1991, 157-8.
[19] Geisler and Nix, 475.
[20] Carson, D.A., The King James Version Debate (Grand Rapids: Baker, 1979), 56.
Source: http://www.str.org/articles/is-the-new-testament-text-reliable#ANCHOR19