Dont know what to connect the red wire to from the headlight assembly replacement

SOURCE: headlight assembly

you will have to remove the front bumper cover to get to 2 bolts and also the grille to get another bolt off also there are are a total of 5 bolts that hold it in. be careful taking it out as you can crack the mounting brackets for the assembly just be patiece it will come out.

SOURCE: How do I replace my 2003 Acura TL passenger headlight assembly?

You will have to remove the front bumper to get to the bolts that hold the head light on
I would not recommend you try this unless you have some experience with this type of work

SOURCE: REPLACE HEADLIGHT ASSEMBLY IN 2000 LINCOLN TOWNCAR

Open the hood and make sure the car and the lights are off.
Remove the plastic protective cover.There are 3 knobs,turn halfway and pull.Put aside and out of the way.
Remove the three pins that are holding the light assembly in place.These are flat rods with a little bend at the end.
Twist and un-plug the lights,now you can remove the whole lens.
The light bulbs can also be removed and replaced from this point.
Make sure all the bulbs are working before you put it back together.

SOURCE: how to replace passenger side headlight assembly on 2001 BMW 325i

The E46 2001 325i headlight assembly is held down by 4 bolts. Question is where they are and how to get to them. The 4 bolts require a 10mm wrench.

There are two bolts on top of the headlight assembly. And two more near the back of the assembly, near the area where you would change a headlight bulb.

There is just one more trick to this. Please refer to this trim: http://e46fanatics.com/howto/howtodetail.php?howto_id=24

This trim hooks on to the side fender, just under the turn signal. You have to unhook this.

Then the entire headlight assembly (including the turn signal) can be slided out together.

SOURCE: Headlight repair on 2003 Mercedes Benz E320

how do you change left low beam bulb on 2003 mercedes e320