How do you replace the headlight bulb on a 1999 Galant?

With the hood popped & the negative line disconnected from the battery look behind the headlight and you'll see a wiring cluster going into a round rubber boot. There is a release button on the wiring cluster. Depress it and remove. You may have to wiggle it back and forth until it pulls out. It's plugged directly into the bulb. Remove the rubber boot. You'll need a short Phillips head screw driver. Look into the back of the headlight and you'll see a wire that's held in place with a screw on one side. This wire is a retention clip and holds the bulb securly in place. (kind of looks like a paper clip that's made into a pretzel) I would recommend NOT removing the screw completely, but just loosen it a couple of turns. You'll need to squeeze the clip until it pops out from underneath the head of the screw. Try not to torque this assembly too much as it is made of a hard plastic and can break off. And remember the placement of the clip as you'll need to put it back once the bulb is replaced. The bulb should come right out. (BTW: this is a H4 type bulb and should not be touched by bare fingertips. The oil from your fingers can pass itself to the bulb causing it to break when illuminated) Put the new bulb in and let it rest inside the bulb housing. (it's keyed to fit in only one way) Here's the hard part... You need to put the retention clip back and tighten the screw that holds it in place. If you've never done this it can be tricky. You'll know when it's back in place when the bulb has little to no play. Tighten the screw and be sure not to over torque it as it is screwed into plastic and will strip or break off. Replace the rubber boot. Be sure to make the boot tight. Clip on the wiring cluster until it's firm. You're done.

NOTE: this looks like it is the same design as my 2000 Galant. Check those instructions quickly to see it my tips would help. I do not disconnect the battery for this. If you are even mildly careful, there is no need. Nothing is exposed to short out. Just make sure the car and lights are OFF. If you disconnect the battery, you are going to be back here asking how to find out your radio reset code with the other 10,000 readers that made that mistake.