How do you reset the "service 4WD light" & the "change engine oil light"

I've heard that if you turn the car on, but don't start it up, and rapidly push in the gas pedal 5 times it will reset the lights. Or maybe it was the brake pedal. Try both.

To reset the Change Oil light turn the ignition on but do not start and then push the gas pedal 3 times.

The Service 4WD light is most likely the 4WD switch on the dashboard. If the lights are acting funny then  the switch needs to be replaced. There is a quick fix for it though. It is most likely that the soldered connections on the board have microscopic cracks. What you do is get a soldering iron and resolder all the joints on the board by just heating it up. GM had used a different type of solder which caused it to corrode. I have fixed mine twice without having to buy a new switch.

i agree with oil light,4x4 light would take to dealer could be a problem with it.