If the '88 is the same as earlier years, remove the wiper arms and all the pivot nuts. Remove the stainless steel trim strip at the bottom of the windshield (screw at each end). Open the hood/bonnet and there should be about four screws along the leading edge of the valance panel you want to remove, holding it to the firewall. Remove those. You should then be able to lift and wiggle the panel to release it from the clips holding it at the bottom of the windshield.