Giovanni, a brand new character to the Animal Crossing series, is an employee at OK Motors along with Beppe and Carlo, acting as the boss and the one you'll talk to for their services.
When you first visit OK Motors, he explains that they handle customizations for your camper and gives you a free paint job. Later, if you talk to Beppe or Carlo , they'll direct you to Giovanni for their services. Some services they offer include expanding the interior of your camper - which can even include a second floor-and customizations to the exterior.
The exterior customizations include regular paint jobs, special paints jobs which may change, and changes to your campers style.