I've replaced speakers in my 1998 and 2004 Frontiers and in my daughter's 1998 Pathfinder. panels go back on readily.
Be aware that these speakers have proprietary mounts and proprietary wire harness, but I just installed traditional 6.5 inch speakers in the door panel locations and soldered on the new harness that came with the speakers. If you're handy, you can figure out how to install universal replacement speakers without an "install kit" from Crutchfeld. Important is to make sure that speaker magnet clears the window, no trouble on mine.
Be aware that these speakers have proprietary mounts and proprietary wire harness, but I just installed traditional 6.5 inch speakers in the door panel locations and soldered on the new harness that came with the speakers. If you're handy, you can figure out how to install universal replacement speakers without an "install kit" from Crutchfeld. Important is to make sure that speaker magnet clears the window, no trouble on mine.