The stains could be anything,
the smoke smell, YUCK!! my wife smokes but not in my car! The car I bought was used and had a touch of smoke smell in it, I ran the heater, with the air venting to the a/c vents too, full blast as often as I could (could stand it) while pulling in fresh air and that helped. I also threw in the glove box a pack of wregglys juicy fruit gum to help with the smell. Now the smell seems to be gone. I'm not kidding about the gum.
None, if I want a faster car I'll buy one.