Problem with 4WD. 2000 sierra k1500 Z71

[truckguy92]

Hey. I just purchased this truck yesterday and it was running good. It has 208000 km on it. Has new tranny and rear end. I went to put it in to 4-HI and the orange light flashed then went out. i stoped and pushed the 2-HI button and it shifted back into 2-HI. I was confused so i checked all the drives and all worked (auto 4-HI, 2-HI etc.) then i was driving home to be safe and the service 4WD light came on. Also, the battery in this truck does need to be replaced as it dies fast without the engine running. (had to boost it today). I was thinking maybe that could be the problem but im not 100%. Or maybe its the switch it self as the orange lights on the buttons do not light up. also the lights on the buttons that say 4-Hi and 4-low do not light up ( they are the white letters on the switches, the Auto and 2-HI do light up).

Any help is greatly appreciated!!!

Also i have a 500 km trip coming up in less then a week. is it still safe to go??