1998 will have a 4x4 module behind the radio, it is basically just two relays in a box, maybe they moved or pushed on wires and it has loose connection now.
GEM(generic electronic module) is also behind the radio and is also part of the 4x4 system, this controls the 4x4 module and the dash switch, so GEM is flashing the 4WD light, because something is unhooked or broken.
GEM controls inside lights, wipers, door locks, 4WD, ect.............so it is fine if all you have is flashing 4WD light.
Pretty easy to push in a radio and unhook a connector, my guess would be thats the problem.
1998 4WD control diagram below