Does II Timothy 3:16 "All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness," apply to reputable translated versions of the Bible, not just the original copies? I want to use this verse to state my point to someone that Acts 2:38 is translated properly and Mark 16:16 belongs in the Bible. Their response will probably be that men translated our versions.
Translations are not inspired, but that isn't a large issue. Anyone -- you, I, or the person you are talking to -- can compare a translation with the Greek text. Even if a person doesn't know Greek or have access to a Greek Interlinear, they still can pick up a variety of literal translations to compare how a verse was translated. When you look at multiple translations you get a fairly good feel for what the original text actually said.
But let's turn this around a bit. If a person says that Acts 2:38 is mistranslated, then he must have evidence from the Greek text to prove that mistranslation. As an example, I run across people who claim that eis in Acts 2:38 was not translated correctly. This then becomes a point of fact that we look up and see how the word is used and translated. When the evidence is examined, we conclude that it was translated correctly. See "Can "eis" mean "because of"?" for one treatment of this argument.
For a good discussion of whether Mark 16:16 belongs in the Bible, see The Authenticity of Mark 16:9-20. What is interesting is that even if this verse wasn't in the Bible, there is more than sufficient evidence in other passages to prove that baptism is necessary for salvation. What isn't being proven by the arguments is that Mark 16:16 contradicts any other passage in the New Testament.