The headlight is easily replaced, but a set of sport going to cost you anywhere from $300 - $400. Most of us open the headlights up and painted the chrome in black (flat, satin, or gloss). I recently did a set using VHT NightShade over chrome and I love the look. It's like black chrome, but at certain angle you'll see brown/purple. It doesn't bother me.
As for the wheel size. 18" wheels mounted on 265/60 tires. 20" with 265/50. The side wall on the tire made up wheel size, to the diameter is the same for the two wheel size.