replacing spark plugs 03 CRV

I have 59k on my crv and noticing poor gas mileage. Would replacing the spark plugs improve it? I haven't replaced them yet since I bought the car and I'm the first owner. NGKs vs Denso? Which is better in terms of longevity and performance? Would replacing the plugs warrant replacing the wires as well? What are the signs/symptoms that the wires need to the replaced? I appreciate any feedback on this post.