What is wrong with my 1998 Chevrolet Malibu?

[michael]

I have noticed it becoming hard to start also it will chug and bog down around 30mph when accelerating. I have noticed it overheating and there is a little bit of smoke when I first start it but only for a second. I have not replaced the spark plugs or the oxygen sensors since I bought it and do not know if the previous owner did either could that be the problem. Help

1998 Chevrolet Malibu with the 3.1 V6 and 157000 miles.