I'm new to most aspects of small engine repair. I have a Briggs 093j02-0006-f1 on a push mower. The person who last used it said it suddenly stopped working. The air filter was saturated with oil at the bottom and was dripping on to the deck. I pulled the air filter off and attempted to start it. It ran for a few seconds and put out a lot of black smoke before dying. I tried squirting some carb cleaner into the carb, but it would not restart. Person who last used it said they added oil. I checked the oil and it appeared to be dark grey and slightly overfilled. I pulled the spark plug it was completely black, I assume from oil. Is the engine a goner, or is there something else I should try?