How to replace the serpentine belt, do you have any diagrams or guides?

Yep, it looks like there is a spring-loaded belt tensioner that needs to be deactivated when changing the main serpentine drive belt out. Here are the instructions on how to do so. Here is the part number for the belt in case you need it:

Serpentine Belt - 12660099

Check out the images (below). Let us know if you need anything else.