I have a 92 tracker, but I think the 98 is the same.
-If you look on the bottom corner of the grill of both sides (where it meets the wheel well) you will see a phillips head screw. take out the screws, but make sure you don't loose the clips that they screw into.
-Moving to the center, you will see another philips head screw up in the middle of the grill. take it out. (there may be two more crews at the bottom where it meets the bumper, I can't remember)
now that all the screws are out, there are two catches at the top that you gotta pop the grill out of. It should now be free so you can work on your lights.
( If in fact the 98 is differant, then scratch all the things I said above, and wait for someone more knowledgable to reply

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