Each Vehicle is printed with a power and toughness, but it's not a creature. If it becomes a creature (most likely through its crew ability), it will have that power and toughness.
Conqueror's Galleon // Conqueror's Foothold
If an effect causes a Vehicle to become an artifact creature with a specified power and toughness, that effect overwrites the Vehicle's printed power and toughness.
Once a player announces that they are activating a crew ability, no player may take other actions until the ability has been paid for. Notably, players can't try to stop the ability by changing a creature's power or by removing or tapping a creature.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Emrah Elmasli & Jared Blando
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
