HOW TO RUN CAR SHOP:
1. Press the green checkmark to let a customer in
2. Make the modification desired by the customer (the faster the better)
3. Press the orange checkmark to confirm, if you did it correctly, it will succeed. If it doesn't, then you messed something up.
Modifications
1. Engine - Customers may want a new engine. Remove the car hood using your wrench, then insert the engine. No need to put the car hood back on.
2. Tires - Customers may want a certain type of tire. Remove the existing tires and place new ones of the type they want.
3. Color - Customers may want their car to be a different color. Change the color using the paint machines above the car.
Other Stuff
1. Keep supplies like tires and engines stocked. $10 for a tire and $100 for an engine.
2. The wrench cannot leave the play area
3. If you ever get tired of the colors and shapes changing so much, maybe give yourself a good smack in the head?