Open the hood and right behind the headlight unit you will see two clips...just pull them up and the headlight unit comes right out.
It is built into the headlight switch.
Inside the headlight switch.
Stand in front of the headlight in question, with hood open notice two black tabs sticking up behind headlight bucket assembly. Remove the two tabs by lifting straight up. The headlight bucket assembly can now be wiggled out of the car and you can now remove the bulb socket from the assembly to replace the bulb. Reverse order for assembly.
under the battery, remove the battery and battery tray
Yes
An alternator from a 2000 Chevy blazer will fit a 2002 S10 blazer with a little fabrication.
You didn't mention what year but the headlight switch in any S10 I've ever seen has always been on the far left side of the dash.
no GM changed the cases
Open the hood, stand in front of the effected headlight, notice the two tabs sticking up behind the radiator support in back of the headlight assembly. These tabs are locks that hold the headlight assembly in place. Lift the tabs up and remove them. Now you can wiggle the headlight assembly out the front and remove the bulb. Reverse for assembly.
Yes
with a dipstick
Remove the bolts from each corner.