I'm more used to doing Photos in photoshop, but I figured how hard could it be ?
As with most things, it doesn't have to be very hard, but it can be if you make it hard.
Also you'll need to learn a few different things; 1) How to achieve what you want with your program (Photoshop) 2) Basics of applying 2D graphics to 3D models (not in terms of 3D modeling apps, but more in terms of understanding how things warp across complex surfaces) and 3) How to implement in AC.
A "how to skin" tutorial is borderline useless. All it will do is (maybe) teach you how to make that specific skin for that specific game in that specific way. There's a million different ways to do this stuff, and all of it starts with understanding the basic tools of you program, how they work and why they work the way they do. If you don't learn that, all you'll ever do is copy someone else; and then what's the point? I've been doing liveries for racing sims since the mid 90s and my methods have changed infinitely throughout that time. I probably don't go about most things in the same way as most other people, but I've developed my own methods that work for me - but that's the thing, I've learned how the tools work so I exploit them to work how I want to work.
For your program, if you don't know how to use it look for tutorials on its tools; a "how to make a skin" tutorial is not going to tell you how to make the livery
you want to make. Generally speaking you'll need to be pretty competent with layers, layer styles and the pen tool, as well as understanding how to manipulate logos properly for best results (ideally you'll be using vector logos). Ultimately, if you can't use the program to create the design and don't put in the time to learn, then nothing else matters.
AC's system is pretty simple because you don't need to pack up any files or anything stupid; you literally make a folder for your skin and every texture file on the car can be replaced if you choose to by simply putting a .DDS with the correct name in the folder. When it comes to different surface finishes (matte, gloss, satin, metallic, etc) it's just a matter of using the correct colours in a different file.
So, with that mumbo-jumbo out of the way... Let's start here: How proficient are you with Photoshop? Can you draw your design with your current skillset, or do you need some help learning that part?