Don't even worry about it. When you have $50 pesos go to the comiseria and pay the fine. When I went to Immigration for my DNI, the clerk looked at my passport and said, "Hey, why did you go to Uruguay so many times?" When I replied that I left every 90 days to comply with the law, he just laughed. "Sorry, no offence," he said, "it's just that nobody ever actually DOES it." Really, it's irrelevant. There's a saying here, "Se arregla." It means, "It can be fixed." This applies to everything. As far as not reentering is concerned, don't worry. They'll let you in, trust me.
Also, your residence certificate requires that you produce proof that you live somewhere, though I'm not sure exactly what qualifies. My bet is that the police will not even notice that your visa is expired. They don't care. (About anything, generally.)
Incidentally, I'm referring to bureaucratic issues, not criminal matters. If you do something criminal you will have very big problems on your hands, so don't try it.