Missing 4WD Light 1988 K1500

[prong2002]

Hey does anyone know how the 4wd works on a 1988 chevy silverado. From what I've read, I've gathered that there is one actuator on the front differential that slides an output shaft to link the two front half cv shafts. I know I have to buy a new output shaft because the outer wall of the bearing inside this output shaft coming out of the front differential is welded to the inside wall of the output shaft where it meets that center axle shaft assembly (sits between diff and two outer cv half shafts). But, I have no light and the vacuum hose coming from front differential is not connected to anything. I might buy the output shaft from advance for $70 tomorrow.