While I have never soldered a rib before I have done a ton of commercial silver soldering. First, solders are most likely incompatible with each other. you will need to remove the silver first to have the best chance of success. I would not try to heat the silver to remove it. The remelt temp is likely 100 - 150 degrees higher that the initial heat. I would file or sand the silver away. The good news is that it is a much higher remelt temp and if there is some solder left that is not in a contact area it may not hurt you. It will not melt and purge into your new joint if you can control your heat well.
