Man, that is a nightmare. Whatever you do, do not try to turn that furnace on until it’s been professionaly inspected! I dealt with a similar mess two years ago when a pipe burst. You can find some really solid advice here on the immediate steps you should take to minimize the damage before things get worse. That guide saved me from making a few dumb mistakes that would have voided my insurance. Basically, you need to shut off the power and gas to the unit right away if you haven’t already. Even if it looks dry on the outside, the insulation inside the furnace acts like a sponge and will hold moisture, which leads to mold and ruins the control boards. The guide I linked explains how to handle the “drying out” phase and what components are usually toast after a flood. In my case, I had to replace the gas valve and the blower motor, but the whole unit was saved because I acted fast. Don’t wait—mold starts growing faster than you’d think in those damp conditions!