98 chevy S-10 sputters and backfires

started the engine on my 98 chevy s-10 and gave it a little gas. I heard a loud popping sound and the engine got quieter and now the truck sputters and doesn`t get much gas. Brown oil spewed out of the tailpipe and the muffler was red hot. I ran out of gas a few times recently and that may have something to do with it. Can you please tell me where to begin to figure out what is wrong with my truck. Big problem, Little problem?