Repairing the body of vehicles in Car Mechanic Simulator 2015 is the easiest job in the game. The only catch can be if you have to repaint it. For that you need to have purchased the Paint Shop for your garage. This is also a great opportunity to stock up on spare parts for the future.
Finding the damaged body parts can actually be a little difficult with a simple visual inspection. Some vehicles are in great shape, and the problem is that they are slightly less than perfect. The up side here is that when it's a body job, all of the parts will be listed. So just check the work order under body, and you'll see the complete list of parts to be replaced.
A tip here would be to replace the parts. Don't bother with repairing them. This will add spare body parts to your inventory. You can then repair these later, preferably with your skill at 90%. Then you will have a nice little horde of spare body parts for buying cars at auction and rebuilding them.
This is as easy as moving the car to the Paint Shop and selecting to paint the car. When you put any vehicle in the paint shop the color is automatically set to the correct factory color. Just send the car to the paint shop, paint it, then retun to the garage. Paint job done.
Keep in mind that if you have purchased a car from Auction and are rebuilding it for sale, painting it is a waste of $500. That's right. For some reason a shiny new paint job will do nothing for the sale value. The only thing that matters in this case is that the body be at 100%.
To help you learn the diagnostics side of Car Mechanic Simulator 2015 as quickly and easily as possible, I have created a few short but comprehensive guides covering each problem category. For a complete listing of these guides, check here:
Diagnostics & Repairs - Car Mechanic Simulator 2015
If you are looking to learn about the early and mid-stages of the game, you may find these pages of interest:
Your Garage, Tools, Tests, & Upgrades, Jobs & Job Management
And if you are wonding what awaits beyond and where the real cash is hiding, check out this link:
Rebuilding Guide - Car Mechanic Simulator 2015