I've been searching for how to replace the stock lens with the zkw lens but no luck. I'm doing the installation early tomorrow and I want to get an idea of how to do it.

BTW can I install an hid kit fog without removing the bumper?

 

No clue about the fogs, but the lenses you obviously have to remove the entire front bumper, remove the headlights then bake them at like 200 degrees for around 10 minutes. Peel them apart then simply pull the metal lens holder off and replace the lens.
Its a pain in the ass and takes time so leave yourself plenty of it.