How do I make a script that displays certain user's names, and renames them, as a billboard GUI?

Developers = {} --Put their name
game.Players.PlayerAdded:connect(function(ps)
    wait(0.25)
    for k,v in pairs(Developers) do
        if ps.Name == v then
            print("Developer is here!")
            while wait() do --wait for their character
                if ps.Character then
                    break
                end
            end
            g = Instance.new("BillboardGui",ps.Character.Head) --remember if they die the gui will go away
            g.Name = "pc"
            g.StudsOffset=Vector3.new(0,2,0)
            g.Size=UDim2.new(3,0,2,0)
            text=Instance.new("TextLabel",g)
            text.Name = "Chat"
            text.Size=UDim2.new(2.25,0,0.79)
            text.TextScaled = true
            text.Visible = false
            text.Position=UDim2.new(-0.125,0,-0.25,0)
            text.TextColor3 = Color3.new(1,1,1)
            text.TextScaled = true
            text.BackgroundTransparency = 1
            text.FontSize = "Size48"
            text.Text = ps.Name
        end
    end
end)

Basically, you're going to want to insert a billboard GUI into the Player's head, then set the text to the Player's name.

Idk if this will work; it's untested. This is really just an example, and it only works when the player first joins the game. I forgot how to do it every time the player respawns.

game.Players.PlayerAdded:connect(function(plr)
     gui = Instance.new("BillboardGUI")
     gui.Parent = plr
     gui.Text = plr.Name
end