If i wanna change my lights to some brighter white-bluish headlights, do i have to replace the whole headlight (with the casing thing), or do i just simply have to replace the bulbs? Im new to this so bear my noob-ness

 

You just replace the bulbs. If you search is tons of stuff with all of your options. I personally know nothing about it, but after seeing so many people do it, I might start looking into it.