Engine 02 sensor

02 sensor

2002 chevy prizm
how do u get to the front o2 sensor? i know where it is and i see it but i dont know the best way to get to it through the top or go under the car?

also do my spark plugs look bad? i switched them. they have 4 years/125,000 miles on them. it's not a good picture but describing it, it has the corrosion lookin stuff. and it's burnt looking
<a href="http://photobucket.com/" target="_blank"><img src="http://i110.photobucket.com/albums/n112/streetvamp85/plug.jpg" border="0" alt="Photobucket - Video and Image Hosting"></a>

http://i110.photobucket.com/albums/...vamp85/plug.jpg

thats a really blurry pic but it actually looks ok.