attempt to index a nil value?

Hi guys, so, I've spent 2 hours (It's 4:30AM now) trying to solve ONE simple error. I've made this script that would give certain users a weapon and a GUI above their head.

The script is pasted in StarterPack (It's a local script), where a BillboardGui is the script's child, and the Textlabel is the Gui's Child.

Please keep in mind I'm a literally all-new scripter and don't know much about usage of variables and such, but this is what I came up with:

local plr = game.Players.LocalPlayer
local name = plr.Name
local admins = Instance.new("BoolValue",game.Workspace.Admins)
local tool = game.ServerStorage['weapon']
local gui = script.Role


if game.Workspace.Admins:FindFirstChild(name) == nil then
admins.Name = name
admins.Value = false
    else
        print("BoolValue already exists!")
end

if name == "NameHere" or name == "NameHere" then
    admins.Value = true
    print(plr.Name.." is an Admin!")
    tool:Clone().Parent = plr.Backpack
    gui.Role.Visible = true
    gui:Clone().Parent = game.Workspace:FindFirstChild(name).Head
    gui.Role.Visible = false
    print ("Added GUI and Tools!")
else
    print(plr.Name.." is not an Admin!")
end

Now, the error I'm receiving is; "Players.XaqiZono.Backpack.Administrators:20: attempt to index a nil value" The error is occuring on line 20, the part where I clone the GUI inside the script, and move the cloned GUI onto the user's head. How can I fix this?

Also; How do I stop my script from executing UNTIL LocalPlayer is loaded?

And, one more question; I don't really know the diffrence between Local script and Server Script, but is there a diffrent way of calling a LocalPlayer via a Server Script?

Thanks!