Plan your changes around what you use, and rely on the most. If the CP is the center of your focus, change it. I think most instrument packages will send NMEA data. I have older Raymarine instruments that are talking to my Garmin 5212 touch screen CP. The AP is extremely important. I even carry a spare. Whatever you get, go more "robust" than you think is necessary. You rely on it way more than you think you will. Again, most packages can talk NMEA. You may need a converter box as with Raymarine, but theirs is