Can I clean/Salvage this board?
I suggest trying this:
Clean thoroughly with a toothbrush and 99% isopropanol (don't use low grade rubbing alcohol- Life Brand 99% &quot;Alcool isopropylique&quot; from Shoppers' is okay). Allow to dry thoroughly (some of those parts will retain liquid underneath- a few hours with it moderately warm or overnight is more than enough). Inspect the board with a bright light behind it/on top and see if any of the traces appear corroded away. If nothing looks bad, try it at this point. It may work. It may work but the switches may be unresponsive or intermittent.
If it doesn't work, the 6x6mm tact switches are too far gone (they're not sealed) or there are corroded away traces, you might want to get some local help- preferably with good desoldering tools and skills or at least skills. None of that stuff is difficult and all the parts I can see are cheap and easily sourced and replaced so if you don't cause additional damage yourself you should be able to find someone willing to give it a shot. Note that if you muck it up, folks will be much less willing to have at it.
And of course you probably want to find a way to prevent that from happening again.