I would recommend changing that o2 sensor asap, I've done three of them with just an open end wrench, you'd be suprised how much they can effect engine performance. As for the intake screen use a pair of snap ring pliers to remove the screen'* retaining ring http://search.harborfreight.com/cpis...iers&Submit=Go
as for removing the screen you can use the snap ring pliers , or two small finishing nails to insert into two of the screen holes and GENTLY squeeze to grip the screen and pull the screen out. sometimes they are fit pretty snug and you have to pull the screen from various locations around the diameter of the screen. be careful because the screen is somewhat delicate .