Payload Skins?

Is there a way to get a skin in a map for the existing VALVe payload without need of a modelling program?

Objective: A RED or Neutral Colored Cart

I'm thinking if it would be feasible to do something like decompiling it, and pointing the QC to a modified texture sheet, and recompiling it as a custom model.

If there's an easier way, I'd love to hear it

Then how will I be able to make the cart red or grey in the map?

Is it as simple as packing the modified vtf with the .bsp?

cool