Car won't start

I have a 1987 420SEL and most recently it's been running like a new car, but last friday it started to miss and I ran the car for a while until I began to see smoke from under the passenger side, my exhaust pipe was red hot!So I replaced the catalict converter now it won't start at all. I replaced the plugs, the distributor cap and rotor. My question is about the firing order.Any way I can get the firing order and can you put the distributor cap on wrong also.
Thanks steve