2001 hyundai xg300 firjng order - 2001 Hyundai XG300

That's called the vacuum control valve.

replace the headlight switch

Have someone rescan the computer wiyh a good scan tool, p1159 is not a good code for a 2001 xg300,

it is embedded in the rear glass

If you were driving a voyager I'd suspect the fuel pump is starting to fail.

clean up all ground wires but you may need both of those items

Here's a photo - remove cap, disconnect connector to bulb, move bulb retainer out of the way & extract bulb - installation of new bulb is in reverse order.
If you want to replace the entire ASSEMBLY, there are three (3) 10mm bolts holding the assy. Remove them, then slide assy forward to access connectors - disconnect them.

yes it does matter, big time.

You start by putting the spark plug wire for #1 on the distributor, on the #1 spark plug. #1 is usually the first plug in the rear on the passenger side. Then figure out which way the rotor rotates, usually clockwise. Then put the plug wires on in the order of the firing order. It is not in numerical order.

If you did not take them off already, just do one at a time.

I THINK THERE IS A STRING IN THE TRUNK ON WICHEVER SIDE THE FUEL DOOR IS AT

Remove the headlight and put it in from the top.