4e is such that I wouldn’t expect anyone who’s mastered the 3rd edition would have any problems figuring it out.

My advice: carefully read all the rules on combat and movement and such and encourage your players to do the same.

Some things have similar names, but just aren’t alike at all (like a saving throw.)

You will have at least one player who skimmed, thinks he knows how something works, but is still thinking of it from a 3rd edition perspective/definition. That will lead to a problem and the more quickly you can clarify the issue for your players the better.