the 12V fridge makes it tricky, if your going to be plugged in at the campground or at home then you are running the fridge. what I do with my batteries is the day before I go camping I charge them to full by turning off the converter and changing my setpoints on my solar controller to full charge. but for you, well it depends how many amps the standalone charger can put out. you could turn off your converter at the breaker panel and use that to fully charge it, but then all your 12V would be running off the stand alone charger so you have to make sure its a large enough amperage for that.
Ideally you can send your converter in and have it converted by WFCO so you still have warranty, or just get them to send it out if you are conferrable doing it yourself and not worry about the warranty as a new converter is less than 300.00 (for a PD 9360) still that's 300 the average person doesn't want to spend. so if your not leaving right away for camping then send it in, if you are then just try it and see how it does. or make sure you have a large enough stand alone to supply the rv while you are using it.