How to fix the SERVICE 4X4 Idiot Light
In 10 minutes patience and some soldering experience and @ $0.0 cost:
Lower your steering column as low as it goes.
Put your gear selector to 1st gear to allow easy dash cover removal.
Pull out your ashtray and carefully "peel" the corner of your dash cover (try to do that at temperatures above 50°F so the cover has some flexibility)
With a flat blade screwdriver remove the module switch out, take the two wire connectors off and your options are:
1) Open the switch clear the solder and re-solder the pins and put it back together at $0.0 cost and big bragging rights to your friends at the bar and your wife or....
2) Purchase the switch from e-bay anywhere from $30+ or dealer in the range of $70 plus still some pride but not a ton of beer money left like from step 1 above.
Put everything back together and you are ready to go. Good luck.
Did I mention ZERO dollar cost?????