IIRC from my 2 distributor cap/rotor changes, it's easiest to remove the air filter box to access the 3 bolts holding it on. Disconnect the flexible air duct from the box by loosening the hose clamp. The air box is held in by push-connect posts that seat in rubber grommets, so you can just pull it right out.

As far as the cat goes, it isn't necessarily unsafe if the cat is indeed bad. One of the ceramic honeycomb baffles inside may have come loose, which could possibly clog your exhaust pipe and cause excessive backpressure. It also isn't cleaning your exhaust as well, so it is more harmful to the environment. Check the heat shielding around the exhaust system to ensure it isn't loose and rattling.