The short answer is that the verb forms in conditionals don't change at all because they are hypothetical situations. However, pay attention to who is who when you put it in a reported speech pattern. This usually trips students up. "If I had been you..." changes to "He said that if he had been me..."

You can't go any 'further back' than the third conditional, so it has to stay in the same form in indirect speech. The indirect form would be, for example: He said that if he had been me, he would have said that I had done it correctly. That's two examples of indirect speech for the price of one, of course.