2001 Chevy Cavalier Tune-Up

2001 Chevy Cavalier 4 cyl Front Wheel Drive Automatic

I think my car needs a tune-up. I have 85k miles on it. I have never had a tune-up since I brought it in 2001 when it only had 3 miles on it. It has had the oil changes that its needed and new brakes and new tires throughout its years. I want to ask how much a tune-up usually runs and does my car really need it?

Also my air conditioning and heat only work when the knob is turned up to level three when its on level one and two it doesnt do anything nothing kicks out. What do you suppose might be the problem?

Thanks for answering my questions!