How do you replace a Head light bulb for Infinity Q45?

You didn't give the year so I am assumming you have an older Q45. My answer relates to 1994, 1995, 1996, 1997 models. Well, its really quite simple. There's a black plastic cover over the headlights that are called air guides. The air guides have to be removed so that you can get to the rear of the headlights. You do not have to remove the entire headlight assembly just to change the bulds, but for the low beam bulb, it would possibly be a bit easier because of the wire retaining clip that holds the bulb in place. Each headlight assembly contains two bulbs, one for high beam and one for low beam. Once you've removed the air guides and facing the headlight. The Hi- beam bulb , you just grab it and give it about a quarter turn counterclockwise to unlatch it and pull it out of the assembly. Now you have to disconnect it from the wiring connector. Just press down on the release lever that you will see and pull them apart. If they are difficult to separate, just use a flat tip screwdriver between the two and twist the blade against the connector to wedge it back and off. Low beam bulb. In the very center of the bulb assembly will be the round shaped wiring plug. It should be encased in a rubber covering or seal. Just grab it and pull it out. Next unscrew with your hand and remove the black plastic retaining ring around the bulb hole. Removal of this plastic piece will reveal another rubber seal covering the bulb hole. From the edges, peel the rubber seal back enough so that you can see inside the mounting hole. Now you should be able to see the wire retaining spring that I mentioned earlier. Use a pair of long needle nose pliers or a screwdriver to detach the spring from its locking points on both sides. You can detach one side of the spring at a time to make it easier. Once the retaining spring is detached, the bulb pulls right out with the rubber moisture seal attached. The rubber seal can be removed from the bulb and of course you want to put it on the new replacement bulb. A lot of words, but its all quite simple, quick and easy. Calvin Bryant