If you’re looking for the duration of copyright, check this. (I got it from another SDMB user in a recent thread on movie copyright).
For your other questions: Yes you may legally print your own copy of the Three Musketeers and sell it. As you can see, copyright should have expired (the Dumas’s have died, haven’t they, the son and the father, no?).
A translation is a copyrighted work in itself, effective for life plus 70 years in US and Europe (I don’t know about elsewhere). If you decide to make a new translation you may thenceforward do with it as you please, just like any author would. However, be careful that you are not exposed to other translations so you cannot even accidentaly take over their solutions.
If you translate a work that is still copyrighted, however, the result will have a dual copyright of you and the original author.
I do not know whether or not there are other regulations on ‘classical novels’ (meaning works on which copyright has expired).