Typically most stuff should be surface mount, which means there are no holes through the board. These are very difficult to desolder without damaging the PCB or components. However, if the PCB has holes through it with solder on one side, components on the other, you just need some solder wick (I use GootWick it’s worth the premium) to suck up all the solder, or you could just heat up each side carefully and take it out, however I’d reccommend the first option.
I think there would be more to it than resistors personally, resistors are pretty bulletproof and can withstand water. They are only passive components. It is more likely a blown capacitor or a blown transistor as these are much more suceptable to damage. It could also be an overloaded IC, but I doubt it as you’ve only blown two channels.
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