I don't have all the answers for you, but here are a few to get you started:
I wanted to remove the vinyl and as it is very difficult without a heat gun and that i want a full artwork...I said to myself, why dont you just fill the littles scratches with sand and stick your artwork on it?
- Is it a bad idea and if it is, why? 
The main drawback is the fact that the cab looks like it has been on location for quite a while. Seems like the vinyl texture would trap a lot of the dust, dirt, grime, cigarrette smoke, spilled drinks, etc.
If you don't prepare the surface properly for sideart, it will curl up or peel too easily. See Rikitiki's
Side Art Install 101 thread and associated videos.
The adhesive on printed sideart is less sticky than some other applications to allow you to smooth it out and avoid bubbles and wrinkles.
The vinyl is thin enough that it will show the texture underneath it.
If you're going to spend the money on printing nice sideart, you can spend the time, money and effort doing a proper prep job
or you can

when it comes out looking . . . not so good.
Think of it like doing a back handspring on cement:
- Doing nothing is OK.
- Doing it all-the-way is OK.
- Doing it half-way is no good.
The clamps for the CP are on the side but i want to haver flipper buttons do you think it is possible?
The thickness of the cab side (3/4"?) plus the panel support (3/4"?) makes it too thick (1-1/2"?) to mount the microswitch on regular buttons.
You could use Ultimarc's Goldleaf buttons since they don't have the microswitch/wires coming off the side.
Use a 1 1/8" hole through the outside of the cab and a little bit larger one through the CP support piece so you can tighten the button nut with a button wrench like this one.

Scott