First, are you using the large sailing rudder? It makes a world of difference in very slow boat control -- you should have one if you don't already, especially for the type of water you fish in!
Second, you're right about the MD 180 not improving your directional control over your older Drive. That can only come from the rudder. BUT, the MD-180 is about 100 times easier and faster to reverse and it can be done one handed while you continue to fish. So if you need to jockey back and forth you can maneuver effectively, in some ways better than with a paddle.
Third, yes you can use the AMD-180 on any of the older Mirage Drive boats. The newer boats have an alignment slot to make it more idiot proof to install the Drive, so the new Drives have an alignment pin. It is cut off to fit the older boats but that doesn't render it useless for the new boats. Here's an image mmiller posted recently showing the pin and slot.
In addition to the MD 180, the new Revo 13s have several features yours doesn't, notably the Vantage seat and Laurence ready transducer mount. The hull is the same though. You can look at purchasing a new Drive vs buying a new boat with Drive.
