Just install new FBI as a proper .cia using your old/injected FBI. If you previous version is in H&S, you can just leave it there since it makes a good emergency backup if you somehow accidentally uninstall the new one. If you had the previous FBI installed as a regular app, you can uninstall it using any method you would like. It's not really worth the hassle injecting new FBI though, as it gets regular updates and works just fine if you treat it like any other home-brew CIA installed on your system.