1998 Mercury Mystique problems

Smells problem
1998 Mercury Mystique 4 cyl Automatic 139000 miles

hi i just picked up my car from a mechenic and i noticed when i was driving home that it smelt like burning plastic. when i got in to my driveway it started to smoke. later on (hr later) i drove it down to my school and it started to smoke again. i parked it and noticed that also im majorly leaking oil. i had it brought to a nother guy and he said that im just burning oil so dont worry about it. (the smoke and smell) my timing chain cover is plastic and i think that might be the smell but could my engine also be overheating beacuse of lack of oil?