Daredevil Dragster

You may tap more creatures than necessary to activate a crew ability.

For a Vehicle to be able to attack, it must be a creature as the declare attackers step begins, so the latest you can activate its crew ability to attack with it is during the beginning of combat step. For a Vehicle to be able to block, it must be a creature as the declare blockers step begins, so the latest you can activate its crew ability to block with it is during the declare attackers step. In either case, players may take actions after the crew ability resolves but before the Vehicle has been declared as an attacking or blocking creature.

If a permanent becomes a copy of a Vehicle, the copy won't be a creature, even if the Vehicle it's copying has become an artifact creature.

When a Vehicle becomes a creature, that doesn't count as having a creature enter the battlefield. The permanent was already on the battlefield; it only changed its types. Abilities that trigger whenever a creature enters the battlefield won't trigger.

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.

Once a Vehicle becomes a creature, it behaves exactly like any other artifact creature. It can't attack unless you've controlled it continuously since your turn began, it can block if it's untapped, it can be tapped to pay a Vehicle's crew cost, and so on.