Can you edit Wii games on PC

Yes, there are some ways to do so.. if you want to edit the actual ISO you can use Trucha signer. Notice though, that editing a single file will invalidate the signatures of the ISO and thus you'd need major modifications done to your Wii - downgrading IOS files and whatever - to play the game. A more elegant way would be to use Riivolution, which you can also use with your original disc (and only with it).

Riivolution can forward calls the game is doing to an SD card - so instead of opening the file from the disc, if will be forwarded to the SD card and open a harmless file there. That's a recommended way by me, it saves you from burning a disc or using backup loaders (unless your Wii is hardware modded).

Please note: no support on how to run a backup ISO, if you do not have an original, do not expect to get help here, Riivolution is the recommended way for what you plan to do!