The hissing when you push the clutch is probably the throwout bearing. They last for a while squealing like that if you can stand the noise. (mine went for months)

Clean the plugs really good (With a wire brush!!!! don't use one of those sandblaster things, the sand can get caught in the plug and fall out when you dont want it to.)
OR just buy some new ones. They get pretty fouled up when it floods.