How do I rename this as the players name?

I have a police car that gives a player a gui to control lights, sirens, ect. Right now, the way it is scripted it only allows one car to work (Finds First Child in the workspace) So to make each car have a unique name so that it can work on each individual car I thought of player names.

So how can I make it so that the car is renamed as the player when entered?

Part 2: Have the script for the lights find the renamed vehicle in the workspace?