2004 Chevy Aveo oil is leaking

i have a 2004 chevy aveo and my car is leaking oil. the engine light is on and when i check the code it said vaccum leak. That code showed up three or four times. I thought it was leaking oil around the oil plug becasue it started after i got a oil change. someone said it was so i went by that. @ weeks ago i went and got a oil change and ask the guy is it leaking around the oil plug and he said its coming form the transmission and it might be tha something need to be sealed. i was wonder if that wat it possible might be.