Craftsman- oil spitting out of the muffler

Craftsman self propelled mower (No. 917.377890) with a Honda 5.5 horse engine. Its' probably 12yrs old & has always run great even though I rarely changed the oil.    Wasn't running very good this summer - I had to have the choke partially on & seemed to idle high but it would keep going.  Last week it finally died while mowing & wouldn't restart.  So I changed cleaned the air filter, changed the oil, & changed the spark plug.  Now when I try to start it, it will fire up for just a second and sprays some oil out of the muffler and dies.  I'm thinking the carb probably needs to be dismantled and cleaned-or replaced.  Would that be the best course of action or does the oil spitting from the muffler indicate a different problem?