I assume you are talking about getting the lid off. I have a 97 and I think the 98 is the same, but when you try to lift the lid, you have to lift the clip side first and slide it toward the clip side as far as possible. Then if you squeeze down on the rubber air intake tube (this leads from the box lid) and tilt the clip side upward it will make it easier to get the non clip side (which has the tabs on it) out of the retaining features. Also it may get hung up of the fender metal but but squeezing the air tube again this will help. When you are putting the top back on, it's pretty much the reverse, but make sure the non clip side is slid all the way toward the fender or else it won't sit properly on the air filter. It just takes a bit of muscle to get it out and back.
I hope that helps.