I´m thinking of changing my left inner fender. It´s a cracked plastic one, but on the right side there is a nice steel fender.

My question is simple and I hope the task is too :)
How do I change the inner fender?

Remove all the screws that fasten the inner fender to the body. Install the new inner fender. This sometimes goes easily, and sometimes it is a tedious task. Be prepared to enlarge some of the bolt holes with a file. Have a jack ready to push the inner fender upward into position. Do not tighten the screws until all of them are in place.

I dont have to take down the outer fender or take down the headlights then? Just the inner fender?

Thanks!

Just the inner fender, that is correct!